Cartoon / logo

I'm starting up a network based on bartering and skills exchange. I need a logo, and a catchy cartoon picture for leaflets and the homepage of the website. The illustrations must show all sorts of people contributing for all sorts of reasons for example language skills, practical skills, knowledge about a particular subject. They all need to be attached to or hang from a tree a bit like a Christmas tree I suppose.
I want it to be friendly and welcoming without being cheesy or too wacky or implying that people are members of a club or social organisation.