Something I've noticed in places here and there (but most notably this screenshot) is that there's not a notable distinction between tiles and elements of the levels you can interact with, and the background graphics. In cases like this screenshot, I'd suggest making the floor/solid areas and the swing-ring things (heh, that rhymed) a little brighter, or at the very least alter their coloration slightly to make them stand out a bit more.
That screenshot in particular showcases a nicely-detailed, but really dull-looking environment; the reddish parts of the ground are close to the same color as the leaves/vines covering most of the background, and the swing-rings are also using browns for their coloration (albeit lighter ones).
Granted, I'm red-green colorblind so it's entirely possible the area looks totally fine to "normal" eyes, but to my own I'm having to make myself notice where the solid ground and swing-rings are, and that's not something a good level should ever make people do.
But again, colorblindness may be causing the colors to look so similar to me, so take the above with a grain of salt if I'm the only one who sees the image this way.
In any case, on the chance it's not my eyes messing with me, clear perception of interactive environs should always be a priority, so even if it's just my own eyes playing tricks I wanted to get that word in in case it truly is too-low saturation throughout the environment.