The most likely cause of this is that you are using a texture whose size is not a power-of-two (128, 256, 512, etc.). SlickUtils then creates a texture by putting your texture onto a correctly sized texture (power-of-two) taking up only 2/3 of the result. I'm fairly certain the SlickUtils' Texture object can give you the correct texture coordinates of your texture. Otherwise you can just resize your texture to be a power-of-two.