Hey Christina! I decided to create my own angelfire account so I could see what's going on here. It looks like angelfire IS cap sensitive so you have to make sure you type the file name exactly how you uploaded it. E.G. if you uploaded it like MOON.jpg then type it like that in the code. If you uploaded it like moon.jpg then type it like that in the code.
Right version - typed the way I uploaded it.
Wrong version - typed differently from the way I uploaded it.
I hope everything goes smoothly now! :)