I have searched the internet for royalty free graphics for my main site which is a student discount site and seem not to able to find any graphics which are suitable for the header page geared toward students.

I was just wondering whether its a good idea to leave the header out of the website?

i have an educational site too (forum) .. check out my site and the header logo, and tell me if u like it .. i can make one for you !!

I have searched the internet for royalty free graphics for my main site which is a student discount site and seem not to able to find any graphics which are suitable for the header page geared toward students.

I can't imagine where you've been looking, there are TONS of RF stockart sites out there!

Try www.sxc.hu - FREE stockart, a few with restrcitions for usage.

For microstock (about $1 /per image) try:
www.istockphoto.com
www.dreamstime.com
www.123rf.com

They all have huge libraries, you should be able to find SOMETHING that works.