I have a Horseman 2 1/4 x 3 1/4 film back. Does it have any value?

Possibly museum value. I have 2 1/4 x 3 1/4 cameras and haven't been able to get film that size since the 1980's and then only Tri-X. Is the back an adapter for a 4x5? It may have more value if so, but still you'd have to cut your own film.

Edit: If it takes 120 roll film, you could probably get something for it on Ebay. Sheet film, not so much. I've got large format on the brain right now - the cameras I have take magazines.

Does it have a Model Number? Horstman made a wide range of camera including panorama and 3D cameras

It may take 620 or even 105 film, both obsolete though 120 was the most popular. It will usually tell you the film size somewhere in the camera. The spools that held the film differed, you can't use 120 film directly in a 620 camera, but you can re-roll the film onto 620 spools.

Here is a list of film sizes

http://en.wikipedia.org/wiki/Film_format

Use Google to find more about your camera, the more information you can find will increase it's appeal when you come to sell it.

Chris