With the Graffiti you can play DOOM and it should be faster than it is through AGA, and a few other DOOM-style games support the board as well, including Trapped and maybe Nemac 4. Also I'm pretty sure you can use it with ShapeShifter or Fusion, the Mac emulators, so you can have a 256 colour 640x480 display with MacOS7 or MacOS8, and you could probably run an older verson of Photoshop with that, and it would be faster than running it on the same hardware without the Graffiti.
To be this useful you need to use it with an AGA Amiga, which can already run DOOM and Amiga-native image editing software well enough.