Editing bg.gif - blank screen - Colorpaper Theme

I am trying to change the look and feel of the Colorpaper theme. After I edited the bg-top.gif file in Photoshop and loaded the new file to the server, I now get a blank screen when I go to my website. I tried switching to another them, but the same problem persits. I just get three funny "greek" characters at the top left that looks like a greater than sign between two squares.