What should you put in header banner?

Hey everybody. I just added a header banner to my site last night after spending awhile trying to figure out the exact spot to put it in and working on the size of it. I was wondering what would be the best thing to use it for? I was thinking clickbank at first but wasn't able to find any good banners for bring the fresh and ended up using a CPA offer instead. I was thinking it might be easier to get a lead verses a sale anyways and making anything at this point is better than nothing. I was also thinking about using adsense but I already have it at the top, middle, and bottom of my post and didn't want that to be the 1st thing people see when they visit the site. I was also playing around with the layout last night and was going to flip the sidebar on the opposite side and thought it looked kind of cool but backwards in a way. All well, could I get some advice about the banner and if this is a good idea or if it will just take away from the rest of the site. Thanks alot