Well, do what a painter would do: Break up your strokes!
If you keep working with the same type of wall/corridor/corner etc., the level will certainly end up looking a bit uniform. How about inserting some completely different tiles? One completely empty, one with a Bomberman-style block grid, a spiral, meanders...
I think it's clear by now that my approach doesn't allow enough control over the map and hence will not be able to provide enough "interesting" situations for the player.
For the final thing I'm pretty sure I'll need to be able to design each room by hand, so I can create complex situations like the ones you suggest. still, there´ll be plenty of random elements in each room and they will be assembled randomly as well, so it should feel different every time you play.
This is probably the way to go, but for now I´ll continue with the current approach by incorporating different room types as well as enemies, so I can get a more global idea of the problem rather than just working on the room generation side.
In fact I've been working on different enemy types for the last couple of days. Pretty basic stuff but I'm still looking forward to putting them in the game