I personally like to display head badges, not exactly something you find often MDing. But I am really into cycling, most head badges I have found have been old junker bikes folks let go to waste in a barn, if I can save the bike then I will display the bike, however most that I have found worth restoring, I normally have an offer on before the work is done.
I also like other little ID tags, could be off an old machine, canoe, stove, or even something that I never figured out what it was too.