I think you should let a student design it, draw it, and then scan it in digitally.
Good fun for the students, good for the winner's self-esteem - and you can scan in all the entries and have the students vote for the winner (if you make it into a contest).
Also, get a local merchant to agree to advertise a banner on the site so your business students get some experience.
Failing that I'd go surf the web for photos.