Oh joy, a key mod is one of the few most wanted things i've hoped for.
I was building a game in your server where you need to kill an evil monster that's terrorfying a mini village and it's villagers, and get his treasure to save the town.
For keys in specific, it would be nice if you could switch their models, for example, a keycard.etc, to fit a theme of a game, but it probably isn't worth trying/too hard.