Hi Lily,
I agree that this would be great. Actually, I believe this was also a topic of conversation at Wikimania. I remember talking about two types of templates:
1) an international template per year that shows that a winner achieved a certain status. I imagine 1a) image was qualified for the international finale (nominated by a <country> national competition), 1b) image reached final round of international finale and 1c) image achieved place XX internationally. This leaves space for countries to design their own templates for place YY in the national competition.
2) a barnstar awarded to the photographers on their talkpage for each of the above categories as digital equivalent of some kind of diploma.
It is a non-negligable amount of work though, designing and awarding them :)
Best,
Lodewijk