Thanks to all of you for your responses! It seems there are quite a few of us who would like to find a way to do this.
I'm not in favor of using caps for the surname, for the reason mentioned - I already have to edit out other people's caps when I use info from their trees and find it time-consuming (and a little annoying, since I invariably miss some of them!)
Using a tree picture would work, but I do have some photos (of ancestral homes usually), documents, and sometimes photos of gravesites that I prefer to use for the ancients.
I do use the relationship calculator, but would prefer something more visual for when I get into the ancestor view.
I will post this message to the Improvements board (thanks for the link!) and see what happens!