I was thinking along the lines of "tally marks", so maybe just a few scratches on the wall, 5 for lowest rank, 3x5 for highest rank.

I'm not good at producing graphics at all, so I'll just link a picture to show what I mean, this is most likely copyrighted etc., so I don't suggest we use it, but somebody should take the idea further.



Whatever we do, I think it should definitely make my profile look like this someday: