You might try to find a phone number or address for a particular airline's Employee Credit Union and see if they could put you in touch with whatever check printing company they use. Deluxe® and Clarke® (sp?) are the two main check printing companies that I remember from my savings and loan days.
It might be, though, that you could only get the checks if you worked for the airline and had your account there, but it's worth a try. If you find out, let us know. I would LUV to have some Southwest Airlines checks.
You can get 200 checks with the same image for $34.50 plus $4.85 for shipping and handling. If you want alternating images you can have up to 4, but each alternate image will cost an additional $10.00. They won't print any pictures that are copyrighted (like from a magazine ad) but if it's a picture you took, then that's ok. Read their FAQ for more info.
I didn't really have time to do a whole lot of searching, but you might want to go to
http://www.google.com and do an advanced search for "personalized checks". (That's how I found the above sit.) There may be other sites that are cheaper.