I have dark wall colors too and our trim is painted white and I think it looks so good. It breaks up all the dark colors. I think if you have a dark wood stain on the trim it is just going to blend in with the walls.
The point of trim is to accent therefore you would want to have the dark walls light trim or vice versa. In my 10 years experience this has always looks the best and always looks wonderful. Also remember to paint the Trim 1st it makes it a heck of a lot easier for touch ups later
Darker trim or tone-on-tone trim will keep the room looking calm and mellow. Contrasting or white trim can look fresh and brighten up an otherwise dark room and is a popular look right now. White trim is harder to keep clean and shows small chips easily - be sure to sand and prime first for the best results.