I usually save as .jpg but they also accept .gif. Art Gallery The thumbnail image (if supplied) should be between 50 x 50 and 200 x 200 pixels and be less than 15 kb in size. Art images should be GIF or JPG format only. The full image should be between 100 x 100 and 4000 x 4000 pixels and be less than 512 KB in size.