isnt a simple popup on the games page the most straight forward method? Adding a temporary category under the account section would mean you can vote at any time after the initial popup/notification.
Im thinking drop nominations altogether and just be able to vote for any alliance in the alliance section and any nation in the leader/community section via boxes you need to submit your entry in rather than picking from a list.
This way it gets broadcasted out to every player not just people browsing the forums. Less talk, more integrated and reaches everyone in the game.
I think these awards are a nice thing to have, and would be a loss not to do them.