So I've been playing a bit of Torchlight recently, and one of my favourite level sets is the Estherian Ruins levels. I think some of the SK level sets remind me of it, which is possibly why I like those levels in SK so much.

I think it would be pretty spiffy if SK got a similar level set. No crazy pile of new monsters/statuses/etc, just new scenery to put the existing ones into. Puzzle elements could include the usual draining or flooding a section to expose a path or raise a floating bridge and so on. Status themed levels could be incorporated with lots of steam and boiling water for fire, murky muck and overgrown fungi for poison levels, slippery ice patches and frozen waterfalls for freeze levels, and shock-conducting puddle hazards for shock themed levels.