The River and other nature would be good.
I like the idea of having a movable river, good one. I'm guessing the attacking ground troops can cross it but at a reduced speed.
Also new traps to go with the river, more goodness in my opinion. For traps some ideas I'd like to see are; when triggered a merman or swamp thing come out of the water and start doing some Kung fu on the grand warden :cool: And another trap idea I have would be some sort of plant, or something, tentacle it would shoot out from the depths, grabs some poor unfortunate miner (or something) and drags them back down to the abyss :caticon::caticon::caticon:
How about Nature as a TH theme for Th12.
Maybe not just the river but other natural features could be introduced, to make a theme. Other nature stuff could be: Living walls, made out of some sort of enchanted trees, as a very special feature the walls could regrow back together during battle, after around a minute. And an elixir troop idea is the Wood Sprite or something along those lines, long tentacle killer plant arms springs to mind again for its attack. And another troop could be a large tree man, bit like a giant but will slowly regenerate his health during battle.
Anyway I'm babbling a bit good idea about the river :)