Worldtree introduced small in-site advertisements, just beneath the cartoon section. In a short time, a series of mini-ads is repeated. If you want to advertize on Lovia's fastest growing social networking site, just contact me. Do keep in mind there's not terribly much space for long texts or big pictures.
An example:
The idea is not mine, actually. I was inspired by Jon Johnson's LTV ad, which is based on the same principle.