The simple solution would be to unpublish the search module which is normally in that position and then publish the module you want to use with your banners.
On our site we have taken off the search box and instead have placed the login module there.
You might however need to adjust the template slightly, depends on how big your banners are. Go careful though because if you adjust it too much it will probably throw the template completely out.
I think you would need to play with the template css file around line 1010 – Search Module. I haven’t had too touch this part so it would be trial and eror. Work on a copy of the file, at least you could then put the original back if it all goes to pot!
Paul