Originally Posted by Myrkrel 
Kevin MacLeod is great - I've used his music in a couple of work projects.
I like the dwarf caravan idea. It could also be goblins, deep gnomes or other opportunistic underground races making some gold off of the "captive audience". I guess it all depends on if any kind of organized societies exist in the dungeon.
Some roguelikes just stick merchants in the middle of dungeons without any regard to realism, so you could go that route too.
Its a bit of joke cliche now. I remember in
Mordenkainen's Fantastic Adventure
But thinking about it there are ways that it can make some sense, some more loosely than others. I'm not thinking of having any drow city underneath but I could do something - or just do what Grimrock did and and put puzzles in to get better inventory.