A lot of good ideas, thank you all for the input. I may end up using several of them in the future, as I have more hobbit (and human) units planned.
I like the horn/night watch. I don't think I will be used on this group, but I'm going to keep it in mind for another in the future. Keys & towers are good. I'm trying to stay away from some of the Warhammer cliches of spoons & chicken (or other fowl) legs.
I'm also thinking about using a rabbit or hare as another idea.
I think the yellow/gold/or at the bottom of the banner looks pretty good with the other colors, so I will probably be using that as a third color. Starting to seem a bit royal!
Background/concept for the hobbit units is still solidifying in my mind, so nothing's quite set in stone yet.