In the age of my youth (pratically when I was just a baby)(When I say baby, I mean I was like 15, 16 years old) I once upon a time hung around sprite comics and their forums and was a former amateur (and I emphasis amateur) sprite artist and editor who never really went beyond minor editting and recoloring. But I lurked around enough sprite critiques and looked through a lot of sprite tutorials to sorta know what I'm talking about! Sorta. Kinda.
Ok, just made this for pure editing practice.
The Master Sword and Hylian Shield aren't my work, I just put them in for completion's sake. Everything else, I made by way of taking apart five different sprites, recoloring the pieces and slimming them down as needed, and putting them together to make a Pokemon sprite version of Link.
Anyway, someone let me know what they think of this, and don't be gentle if there is something wrong. Like I said, it was for practice (though I'd happily use this if someone liked it and wanted a Link with Pokemon sprite for some reason).
And like it or not, I hereby dub him Link, the Hero of Mons.
Edit: Made some changes already based on some good criticisms I've gotten, so I put the edited version here and leave the original for comparison.
Hmmm. Well, first things first, mixing sprite bittages/styles is a huge no-no. I'd say that you should take out the shield and sword and try making one from scratch if you could, but that'd be asking for the impossible. XD; Pokemon trainer sprites also don't offer much in the way of swords and shields in the game, much less anything that resembles either, but perhaps you can edit the shield and sword to make it look less like 64 bit and more like 32 bit? Or maybe just omit the two entirely until you build up the skills to make a better fitting shield and sword.
What also feels off is that there needs to be more shading overall. Like Link's tights for instance -- I know that his tights are white, but there's too much white in his tights. Add in some more grey for shading especially around his knees, shins, groin. There needs to be some darker greens for shading on his tunic and hat. Also, I'm not quite sure but there seems to be a few stray pixels on Link's hat but it could just be my screen acting weirdly again. But if there are stray pixel lines, you should fix that up some, because it makes it look like his hat is shiny. His belt needs a little extra shading too. His boots also need to be fixed up some: The foot that's not under the shield only needs a little extra shading, but the other foot that is under the shield needs darker shading. (Or it could be the other way around. I don't exactly remember which trainer sprite you're using as a base for Link and it'd be helpful if I could see for a comparison.)
Also, Link seems a bit too tall in comparison to other trainer sprites, so perhaps you should make him a bit shorter by a few pixels?
And finally, add an outline to Link - a grey outline around his tights, a darkish green outline around his hat and tunic, a brown outline around his boots and belt. Not a full outline though! If you look at most Trainer sprites they have this outline thing going on, but it's never a full body outline. It's very noticeable around areas that have the lightest hue, and only there in the darkest of areas to emphasis the shadows.
On that note, most sprite artists would avoid using white at all and instead opt for a very, very light grey that's a few shades away from white. The same goes for the color black. Black and white are only used as extremes.
Another round of practice yields fruit, and I need quality inspectors to make sure said fruit ain't rotten. So, today's project was Mr. J, the Ace of Knaves himself:
I personally like what I managed to do here, despite the small size making it nigh impossible to put a playing card in his hand (trust me, I spent a solid hour trying) the way I wanted. So, anyone got any critiques to offer?
Edit: Ok for some reason this came out ridiculously tiny, despite coming from the same sprite sheets I've been using all along. Dunno what's up with that. Scaling worked out decently well though, it might even be an improvement with regards to the lapel flower.
Edit the second: The Joker looks plenty amused as always up there, but the post looked lonely without a Harley in need of revving
And of course, Harle needs her babies.
Something about Joker's face seems a bit off and blurry, like the sprite has been resized? The red on his mouth seems a little too large, but if you make it one pixel smaller it'll look too small on his face. I'm not really sure what to say that can fix that, but maybe it looks off too me because the sprite looks like it has been oversized. The purple coloring of his suit overall needs a little more variation in terms of shading, (like the darks should be a little darker) but all in all the base coloring is good.
Harley's looks alright too me, but the black parts of her suit is too dark. Earlier I said that you should avoid using too much black, so you should go for a dark shade of grey instead, like what the Team Rocket Grunts are wearing. (Only using black to emphasis the darkest of dark colors.) Also, the white cuffs on her hands don't seem to match very well with each other: The one that's petting the Mightyena seems too blurry whereas the white needs a little more shading. (like light grey.)
Alright, today I got asked for requests from a friend just to get a character or person to try and make. From Sue Sylvester, I received a request for Gohan circa the Cell Games. She forgot to say if she wanted normal, SS, or SS2, and by the time she DID I was already working and didn't notice. So, I just made all three 
Normal:
Super Saiyan:
And by far the hardest to get even sorta right, Super Saiyan 2:
Overall these weren't so hard, except redoing the hair over and over to get it just so. I started with a generic Black Belt trainer sprite, turned his gi into a Piccolo/Gohan style purple thing, changed the obi, added the wristbands, reshaped and colored the feet to make their weird elf-shoe things they wear, etc. The head is from a totally different sprite, and as stated a LOT of changes went into the hair on all three.
Normal Gohan's hair looks alright, but the Super Saiyan hairs need to be fixed up some. Again, don't use black for shadows -- use a darker shade of yellow instead.
His outfit, particularly around his legs need some darker shading -- A little shading around the front leg, but there needs to be some darker shading for the leg in the back. There seems to be extra stray light pixels there too, so you should get rid of those too (cause those are throwing me off XD). Also, there seems to be a pixel off by his thigh that's in the front. A little shading around his torso wouldn't hurt either.
I been looking for the right parts to make this one ever since I started on Joker up there. So, here is Batman:
Hardest part of this was the cloak, everything else was just minor reshaping and recoloring. Oh, and the cowl wasn't simple, though hardly difficult.
Edit: Altered the color on the arm-blades a bit, they didn't show up worth crap on black backgrounds.
All, in all, this sprite looks all right to me -- maybe get rid of the black lines up there on his cowl to make it look more consistent? The torso needs the slightest bit of extra shading there, but I like how you did his abs there. The right arm looks a bit off there though and I'm not too sure how to go about fixing it. The shading around his legs and groin look a bit off...but his left leg looks alright to me. His right leg however, needs a a better outline around his thigh or otherwise it looks like it's blending in with the cape. Maybe if you add in an outline to his right thigh, the legs might look better overall?
The cape however
looks awesome to me.
Also, after look around a bit, I found this Pokemon Trainer spriting guide that has some decent tips as to making custom trainer sprites:
http://pokemon.livejournal.com/138050.html
By the by, which program are you using for spriting? I find that using MSpaint and photoshop are best to use.
Its one of the reasons I suggested the tattered ends when we were plotting this out, the tattered ends make it easier to rationalize whatever rough edges are left on it as being tattered or worn themselves