You should use a texture of a power of 2 for the size. Odd sizes may not display properly or even cause problems. That is, instead of 768, use either 512 or 1024. Instead of 384, use either 256 (the fastest) or 512. 256x256 is the fastest, but I otherwise see hardly any speed change. I suggest going no higher than 1024 on a side. Having multiple skins on the same model means having that model take longer to render. From a test I did, a model with 16 skins rendered as bad as ten models with 1 single skin. The actual results showed 62% faster rendering.