One of the places I checked out yesterday was Big Tree Cafe, its an art gallery and a restaurant with indoor and outdoor seating on the edge of the Mekong. This could be a cool place to kill time if you ended up spending an extended stay in Luang Prabang and you don't want a distracting atmosphere ruining your focus. I ate their fish burger which felt more like a fish salad in a bun then the greasy fried fish I was expecting.