I really like the 'pieces' bitfield in the rpc, and I'm having the idea of not just showing if a certain piece is downloaded or not, but also to show how available it is in the swarm. This could be the number of peers who are offering this piece, but it could also be something more abstract, like a number between 0 and 10 or something.
I actually cannot think of any use of this feature, but a table of slightly changing colors and/or numbers would surely look great. (: