System I wish! I did it but with template edits.
Someone even gave me code so each category had its own logo by the title on the category page, and all child pages.
But it's all template edits and EXTRA.css.
Dang. I thought there was an add on for this. I used a mod for vbulletin for years that did this. Really handy for customising a site and making it more user friendly. Not sure I can be bothered putting in dozens of if statements in the templates to get it to work.