Hello,
thank you for your comments! I appreciate it very much. Now some replies to your suggestions.
About washes and drybrushing, you are in a way right that model needs some depth. I don't have enough skills to create those realistically so now I left those out. For next model I certainly will try out something.
Scratches, yes, too evenly and some of way too heavy! This is something that you should have some kind of algorithm for it

You either apply too few or too many and always too evenly. Well, next one will certainly have smaller and fewer scratches.
Crockett, I take your comments about lighting and background seriously as I'm just learning photographing as well.
Thanks again
Niko