WordPress - Unique Header Image

I'm trying to make it so a unique header image will appear on the following two pages within vanwingerden.com:

http://vanwingerden.com/fundraising/
http://vanwingerden.com/finished-plants/

Currently, it is showing:
http://vanwingerden.com/wp-content/t...ries-image.gif

However, I'd like it to show:
http://vanwingerden.com/wp-content/t...am-nursery.gif

Attached is the header.php file. (I tried creating an 'elseif' statement in it, using wordpress's codex for conditional statements, but don't know PHP very well and had no success. I deleted my attempt.)

Here's the CSS:
http://vanwingerden.com/wp-content/t.../turquoise.css

Thanks a million to anyone who can help!

I solved the issue using a WordPress template that allows me to change the "skin" of each particular page. Thanks!