Add logo in multiple vhosted domains

Hello,

I'm wondering if there is a way to add for example a logo on multiple vhosted domains without having to write the code on their sites. Basically I want apache or something to add "Powered by <image>" to all my vhosted domains on my server but not change the code in vhosts html files. I hope you understand what I mean. How can i do this?

The server is running Ubuntu 10.04, Apache2, PHP5

 

This should give you the idea: http://www.howtoforge.com/forced-ads-on-ispconfig-with-debian-etch