Problem with slick v270. TextureImpl.release() calls InternalTextureLoader.clear(String name) with original resource reference, but InternalTextureLoader.getTexture(...) stores modified references (with alpha and flipping data added).
So, the following code fails to render image:
Image i1 = new Image("myImage.jpg");
i1.destroy();//texture is unloaded from opengl, but remains in internalTextureLoader
Image i2 = new Image("myImage.jpg");//gets invalid texture from cache
i2.draw();//draws white rectangle in my case
Fix: TextureImpl should somehow store modified resource name and use it in release method.