There are 3D images out there related to Final Fantasy VI. They are shots from when the developers at square were playing around with the Nintendo 64's graphics engine to see what was possible for Final Fantasy VII(before they made the jump to Sony). The images are off Locke, Celes and Terra, but there's not much else to them.

Here's some screenshots from the demo's: http://www.jzcool.net/ff/ffsgi/ffsgipics.htm