You may change the size of the images to increase details, but the aspect of the image needs to remain the same. Furthermore, all images need to have width and height to be power of 2 (i.e. 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, …) The maximum size is limited by the graphics card (and the graphics card memory) and must not exceed 2048. We recommend to leave the image size as it is (or by max double width and height to be on the safe side).