Regardless of theme, I'm going to put this here. I've sorted the palette a little, so it's a little more organized now. Note that I put all the different shades of green into one palette line, so they're all the same sort of colour.

Also, I haven't added SE's sucker tubes yet, but only because I want to add a few necessary bits like corners before I stick it in.
So, if possible, use this image as a base colour-wise.

EDIT:
Also, wondering about the water tiles n0 added. The text signs work great on an angle, but the water tiles are a little unusual, and wouldn't work with Water Block events. What do the rest of you guys think?