UPDATE: Thanks to Chik Quintans for pointing out this might be a RESPA violation. You can provide a room for the photos but the Realtors would need to pay the photographer directly. Interestingly enough, Karen Deis is in the process of writing an article on this marketing strategy so I will share more information with you as I get it.
A local competitor recently brought in a professional photographer and offered a free photo shoot to all the Realtors in our area. For one afternoon, the photographer was in the mortgage company office and offered photos on a first come, first serve basis. Refreshments and networking thrown in for fun.
Brilliant, simply brilliant.
If it weren't my competition.... I would do this in a heart beat and then offer it again every 6-9 months.