Google Swamp.
Google Swamp Autumn.
Google Swamp Winter.
Don't tell me these wouldn't look beautiful in spiral knights (neutral, fire, and ice themed swamp stages respectively).
After talking about water themed levels, while most of the suggestions are aimed at fully submerged gameplay, I think that levels with waist-high bodies of water would be fantastic too. Calling the levels swamps would get the message across quite clearly what is going on in these stages.
Also, I think swamps could be a fun lockdown stage.
Thoughts?
+1