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Jon's textures page
Sometimes, I create textures. Most of the time, they are crap, but sometimes, they are nice. Especially when I start from some other art (which is always re-usable). I place these textures in the public domain -- do with them what you will!
Usually, there will be diffuse, gloss/shininess and bump maps; you can calculate the alpha map from the bump map in Photoshop using the NVIDIA texture tools plug-in.
If nothing else is stated, you can assume that the textures are in high resolution (2048 usually), high quality (tga usually) and seamlessly tiling.