I've been using Gimp for a long time, but this was my first attempt to edit the contents of a picture. I entered it in a photo contest to meet my favorite athlete, and I'm in second place so far! What do you think?
(note, the contest is via facebook, so you will be redirected there)

https://www.facebook.com/photo.php?fbid ... =1&theater

This is my own humble opinion. I'm no artist .. not even by the extreme stretch of the imagination. But I'd experiment with some shadow on your cracked glass. As it is it appear to have a very flatness about it.

That's incredibly well done. Some shadow may be helpful too but it's very realistic anyway.