There's a KOA and a restaurant/trading post within 50 yds. of the entrance to Devil's Tower. Nothing fancy, but its a 50 mile round trip from Devil's Tower to the expressway. There's a gopher "village" just inside the entrance to the park, and take binoculars because there's usually somebody climbing the tower. Several places along that 25 mile road to stop and take pictures. When you actually get there, you're too close to get a picture of the whole thing. They show "Close Encounters" every night inside the Trading Post.
There's a walking trail around the base of the tower.