Half the fun of the postcard thing is receiving pictures from (and sending to) faraway places, so personally I'd hope we don't separate EU/US.
Also purely my personal opinion, I think the absolute beginners and the experts should be 'mixed up'. It's not a competition (is it?,) so as a beginner I'd consider it an honour and inspiration to receive an expertly created print. Of course the expert who receives my rubbish one may not be so keen, but not everyone can be a winner
However it's organised anyway I'm sure it'll be great - looking forward to it!