Raymanni said he'd do some updates to his tilesets, so I wanted to post some comments and suggestions before they go in.
I think visually they are really great, and it's quite impressive especially what the Gore tileset can do with just 14 terrain pieces. It's very versatile. My comments are mostly suggestions about usability.
Lab tileset
When building the remake of Let's Block and Blow (Lovely 13 I think), I needed some chopping and grouping to piece some of the pipes together. I think for the small ones it's not really an issue, but for the thicker ones some extra pieces would come in handy. In particular, what would be nice additions is corner pieces (90 degree angle), junction pieces (this actually works best as a regular pipe piece with a triangular ending), and end pieces so you can make the pipe just end somewhere. What might also be nice is a piece joining a big with a small pipe piece, i.e. getting very narrow. Btw, you don't really need vertical and horizontal pipe pieces as in Lix you can rotate pieces.
Maybe one or two bigger blocks when you need to fill up a big chunk of solid terrain, though the square blocks that you got already work quite well.
The animation of the water could maybe be improved a little bit, or maybe you've already done that.
And the upward elevator is a bit useless right now, as the lix get stuck at the top. Maybe a top part moving the lixes to the side (or two, so they get moved to both sides, depending on where they enter the elevator) could help here. The downward elevator could also do with this kind of piece.
Gore tileset
Don't have much to say here, actually. It works really well.
Maybe a few smaller pieces of goop to put onto terrain in a more subtle way?
Again, the water animation could be a bit more fluid maybe, and somehow a bigger visual distinction between the trap and the exit eater would be nice. I'm not sure how to achieve the latter; the exit eater could maybe have a somewhat more friendly look (big googly eyes? lips?)? Or the trap eater blood on its teeth? Not sure.
Toy tileset
I think it'd be nice to have a few more different block sizes. I could make use of a wooden block that's half the size of the letter blocks, and maybe a block double the size of the letter blocks?
The chalk pieces are a bit annoying to use. They are all very small, and in particular I don't quite see the use of the tile linking two chalk pieces. I think just having a central piece (4 times as long as the current piece), one or two end pieces for each side, and then two or three ready-made chalk platforms of different lengths would work better. Also you don't need vertical and horizontal versions again as in Lix you can rotate pieces.
It's actually an interesting question what's better to provide: platform pieces that you can stick together, or ready-made platforms, that if necessary you can chop apart with grouping if you need a platform of a different size. I suggested both because I don't know what's best.