Notaz, ive experienced some graphical isues with 2 of my psx games, both happen to be 2D, one is Captain Commando where as soon as you start fighting after a couple of minutes your enemies tranform into some kind of blocky pixels, really strange, and on Broken Sword 1 sometimes there is also some strange pixels apearing in the screen during gameplay.
Edit:
I forgot to mention some problems also with Samurai Spirits 4, the botom part of the characters are mising, they apear and disapear every few secconds.