parked domain logo variable

How can I show different site logos based on the parked domain in use?

I'm using Dolphin as a prayer platform.  In some cases, I may want churches groups to simply have their domain point to their group page.  Is there any way to park churchgroup.com on willpray.com and have it land on their specific group page, and here's the key... show their logo instead of the willpray.com logo?  So, if people go to willpray.com they see my logo, if they go to churchgroup.com they see the church logo and land on their group page.

I just don't want to load many instances of Dolphin for various group members.  It might be acceptable to have churchgroup.willpray.com for the address... really trying to solve the logo variable challenge here.  I realize I'll have to set up the parking and such with cpanel.  Talk to me about the logo.  I'm hosting at Arvixe on Dolphin 7.0.1.