Avatar sizes
>reduce everyone's base avatar sizes
>permit trading X amount of credits for X additional pixels in height
Username changes cost X credits
Text title changes cost X credits
Image title changes cost X credits
Additional Text title costs X credits
Additional Image title costs X credits
Reset reputation costs X credits
Introduce "flairs":
>much like moods, but they change the style of one's post (such as post background, outline, adding a certain effect - personally I would go with a faint background change, similar to what you see on Battle.net forums with MVPs and staff, but far less drastic)
>give every usergroup access to a default flair (e.g. donators get a slightly gold-brown-ish post background, minions get a slightly greenish post background; to distinguish from normal flairs use a specific pattern - such as stripes or something)
>introduce special flairs for X credits (certain solid colours for a bit less credits, certain special effects and patterns for more)
1 min paint job to illustrate what I mean by flairs:
This is obviously very crudely done, but if *someone* spent 5 mins tweaking the CSS markup, it wouldn't be hard to allow users to select a flair somewhere that would add a certain class to their post and with it a specific css markup