What to put in a leopard gecko tank?

My leo is about 6 years old (not quite sure exactly how old), and lives in a pretty small tank. At the moment he has a coconut shelter, large pink shell, 2 smaller shells, small log with holes in it, and a triangular stone water dish. He has a light and a heat pad (covers about 1/3-1/2 of the tank). Is there anything else he needs? He gets very confused if anything in his tank gets moved too much, but I was just wondering if there were any other neccessities?