Since categories are redundant (relative to keywords) and usually inadequate and therefore problematic, how about "auto=categories"? Specifically, if a customer does a "category" search, behind the scenes, the site would use an algorithm based on keywords etc. to present that "category" of images to the user. This would eliminate the time wasted by contributors picking categories, and it would also allow the agency to refine, add, and improve the results (via algorithm improvements) of "category" searches by customers.