header image

Hi everyone, Please can someone point me in the right direction. I have a forum setup on https://community.aquarist.com with my logo which is great, the problem occurs when i try adding 4 simple .png's to the banner and center them like the attached "community_header.png" i knocked together in...

I would like to create a "Header-image" (photo) very similar as show here: Have You Seen ... ? | Express Plus Company But I would like to have a different image for each different "Forum Category" (a different photo for each Forum-Node). Does anyone know of how to do this ? Many thanks! :)