Customers stay on a restaurant's Yelp profile a full 2.5 times longer if that profile has pictures. So...pictures are kind of important!
Don't go overboard and add a photo of every item on the menu, but do make sure to include pictures of your best (or most attractive) dishes.
Also, include pics of the restaurant interior so customers can get a feel for the dining experience. If you add a photo of the restaurant exterior, your new customers will have an easier time when they're trying to find your place.
Lastly, feel free to include photos of staff to make your restaurant seem more authentic.