Actually, while we are at it, maybe add a few hooks into Lua that allow for modifying graphics: For instance, cutting off a section of the sprite, or creating new sprites by using multiple images, or even changing where the pixels positions are.
Edit: To add another suggestion to this, perhaps lua that only affects display on clientside: For instance, changing the appearance of specific enemies for easter eggs (so if someone is in a "holiday" mode, one would be shown variant sprites and textures that fit the mode. Adding hooks for existing clientside settings such as checking if OpenGL is on, or if one is using MD2s. I already know of a way I could use this (making standard player sprites invisible when MD2s are on, to load the textures in the wad file without having multiplayer users be stuck viewing the textures instead of the sprites if they aren't using MD2's. Heck, having checks to see if a specific sprite has an MD2 model would be great for that too.)