Did you not get the thing that said "The Lone Wanderer found the wastelands an inhospitable place...blah blah..."? That's the end, the only end there is. It changes a little if you're good or bad, and a few of the side-quests change what it shows. If you're good and you freed the slaves, it shows a repaired Lincoln Memorial. If you didn't and you destroyed Megaton, then it shows a destroyed Megaton to symbolize your badness. That's pretty much all there is to it.