turn on the show_missing_textures feature of the custom driver, then start up your game. Go to the area you want to find a texture for and just kinda run around. If it is a battle area, get into a fight in the proper area. Now exit the game, and open the file called APP.LOG found in /ff7. Scroll down and you will see missing texture warnings, these give you the proper filepath you will need to place your PNGs into. The filename of your PNG must also match the filename of the original .TEX file.
