I don't know of any outside services, but what kind of pictures are you looking for within Disney? Disney already provides Photopass services in the parks and resorts. The personal sessions at the resort are very well trained photographers. Not only do they need to be with Photopass for 6 months, they must provide a professional portfolio and additional interviews. Plus they've worked in the resorts for a long time now, they know the ins and outs of the best shots.