Why can I only upload a real picture as my avatar?

By default all games will randomly get one of the in game hero pics. You can change your avatar if you buy the package to let you do this.

There does seem to be some issue though with changing images. Many people find that they cannot change them. I myself have found that I could change avatar images from one device but not from a different phone even when trying to use the same image.

If you have trouble after buying the package then please report it to the game developers using the in game support option.