Hi olio, that has to do with the way that video cards work.

If you were going to use that texture for a "full render" calculation like a ray-trace render or something like that, then it would not really make any difference.

But if the texture is to be displayed by your video card in real time, there are some optimizations that it can do for textures that are a power of 2 like Will mentions. I'm not sure that this is very significant anymore with more modern cards though.

Originally it used to be that 3D video cards would actually only support textures that had a size of a power of 2 (like one of: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048) and nothing else, so especially things that were oriented towards producing textures to be used inside of games would be really focused on that.

- Michael