need background image changed in thesis

I have a thesis installation that is a little complex. I had someone take my html website and turn it into a blog using thesis theme. we then added a blog link. I need the background changed on all pages and the blog. ## Deliverables 1) All deliverables will be considered "work made for hire" under U.S. Copyright law. Employer will receive exclusive and complete copyrights to all work purchased. (No 3rd party components unless all copyright ramifications are explained AND AGREED TO by the employer on the site per the worker's Worker Legal Agreement). ## Platform wp