I might as well spoil you guys with this discovery, or, "easter egg".
Turns out that the field where you recruit Vincent, has Sephiroth in it. If you make him visible he will be standing right next to Vincent's coffin. Then if you trigger an unused action by him...
...he slowly turns his head to the left, while being moved so he appears to be growing. EFFIN' CREEPY (and awesome)!
This action is not associated with any scenes, so we can only guess its usage.
I can think of three occassions where this fits.
1) Nibelheim flashback. With the background turned black, the image of "creepy" Sephiroth would foreshadow the threat he is becoming during his extended reading session.
2) Nibelheim, present. A way to foreshadow his presence in the basement, where he will meet Cloud and talk about the Reunion. Again, background most likely meant to turn black.
3) Recruiting Vincent. When Cloud (or Tifa/Cid, whoever is the party leader) tells Vincent about how Sephiroth went mad, the screen turns a different tone, while Cloud gestures, telling the player that Cloud is telling the story. This would fit perfectly with the appearance of CREEPY Sephiroth.
Wow, to think we'd find yet another unused occassion of Sephiroth being planned a dramatic sequence. Unlike with the giant Sephiroth in Sector 7 though, which Motomu Toriyama was in charge of, this is a field that Yoshinori Kitase apparently was in charge of.