Most of the games have unique styles to them, so it's hard to make a contest "universal" for all games other than an artistry based one.
On that note, I have a few game specific non hand/computer art based
contests for future games:
Side note: To help with deciding winners, submissions could be fan reviewed like the SW art contest.Atelier Rorona:"Create your own Alchemy Recipe"
- Points would go toward originality, humor, effect, purpose, complexity, name, etc...Ar tonelico 3:"Create your own hymnos lyrics"
-This would revolve around creating a reyvatail song that involves anything from previous games to certain emotions, topics, issues, feelings, etc... basically it would be like making a poem
You could also create accompanying music too (if your musically inclined), though it would be slightly harder to post and reviewDisgaea 4:"Create your own overlord"
- This would involve creating your own overlord and story chronicling their rise to power as an overlord. Again, points go to originality, humor and awesomeness
I could give examples of each if people are interested for clarification purposes