I've been in a forum where apart from the usual post ranking system, we also has an equipment system.  Granted, the forum was not just about RPs, but the equipment system had quite good uptake.

For each post you would get a point.  And you could use those points to buy things that appear under your profile as text.  For example, I just used 50pts to buy a Newspaper Hat.  And last week I bought a Bulletproof Vest.  My profile would look like this next to my post.

SilverRain
Headgear: Newspaper Hat
Armour: Bulletproof Vest
Accessory: Red rose

My profile would have a list of things I had already bought and I can switch between them.  Certain sections such as Spam, did not award points for posts.  The equipment system did occupy a bit too much space though - especially for those who bought something for every slot.