Hi ACHTUNG MINEN,
Have you tried to upload a different photo (instead of the one you wanted) or one of FlyOrDie's avatars?

Maybe the photo you chose is too big in terms of kilobytes. There are free sites on the internet to make your photo smaller (in terms of kilobytes. ) 

You can upload *jpg, *png and *gif files.

Last but not least you could also test whether it works with different browser.

I hope that some of this will help you.
Wishing you a pleasant day and good games!