I believe it is just JPG and BMP, but you can try. I made the one shown and found two others. The others would not load. All were jpg of the correct size. The dimensions in the manual were crazy. They said no bigger than 4000 x 4000 and 6MB. I think that is way too big. I think I made mine 900xsomething like 530 and it was in KB. Experiment.Makes me wonder if we can load animated gifs? Don't think so, but it would be neat if we could.
What are the screen dimensions? I need to do a nice one that fits properly.
Right now my wife just has a simple picture of her dog.