All the following textures are especially adapted to realtime 3D constraints:
textures have all a power of two dimensions such as 512, 1024 or 2048
almost all textures are seamless (cyclic)
each texture comes with a normal-map (ex: texture_name_DOT3.jpg) that can be used in bump mapping effects
(see tutorials on this topic: Normal-Maps and
Bump Mapping)