http://en.wikipedia.org/wiki/Kitchen_Confidential talks about refrigerator space and other constraints common to modern restaurants. Whenever you order that chicken that's on the menu together with shrimp, lobster, steak, ground beef, pork chop, pork loin, tuna, turkey, salmon, tilapia, etc., you risk ordering something that's been re-frozen multiple times, stuck in the back of the fridge (the more exotic it is, the higher the chances are that it's been there for a while, alligator kebabs and ostrich burger patties least likely to be fresh), and handled multiple times by line cook's hands while he reaches into the fridge to retrieve stuff for other customers.

this is really against what most restaurants should try to do. I'd rather have a place make 10 dishes very high quality than 50 ok dishes. With a large menu its very hard to provide quality and consistency.

I find it pretty common given a list of foods that I like, the one with a good picture is the one I'll most likely order. Having more pictures may or may not benefit the restaurant though...

Use of a few pictures now could lead customers to buy a higher profit item, or an item that is much easier to keep in stock in large amounts.

Use of pictures for all items means that the customer will likely expect the food to the table looks like the item in the picture. This could cause some issues with different cooks or item substitutions.