I found a great plugin for $29 that is a super powerful ad rotation system, but it also will help you design the artwork. So you have all the things you need in one place.
You can sell ads based on
Pay per click
Pay per view
Pay per time
Group ads into a group and put them anywhere on your site
Trigger when a where an ad shows up.
FREE STUFF
This month at If you go to Themeforest.net
you will see in the middle of the page they give away a free Wordpress theme, free music, free Adobe templates, free 3d art and more. No shenanigans. They give away one free item a month