Truevision Targa(.tga) files are used in game as the format for textures.
As with similar file types, tga files can be edited with most Image editors, so long as the program has support for tga files. As the format has support for alpha layers(i.e transparency), the game uses this layer to apply effects to the texture in game(such as a shine). For more information in this, see TXI Files.
-While it is possible to make higher resolution versions of textures for this game, their size must scale with the original. If a texture is 128x128, then it has to scale up to 256x256, 512x512, and so on.
-While almost any texture in the game can be given support for effects(aside for gui textures) if not having one already, only one effect can be added to a texture. Such as, if on a player head, one wanted a portion of the texture to shine, and for the character's eyes to glow, that cannot be done without much more work.