Actually, your levels are so fun I couldn't resist going on
so, skipping #17 for now.......
Level 18: great to see someone else using my Prince style! Nice level, too, though it's still pretty obvious how to get past all the obstacles.
Level 19: ok, this is where it really starts to get tedious; I feel I've had exactly the same level before only some of its previous incarnations (e.g. Level 10) were a lot more interesting than this one. Sorry to be so blunt.
Level 20: I'm sorry..... I was going to make up for my rudeness about Level 19 by praising this one to the skies, as it
nearly deserves. Trouble is, you've got a major backroute involving dropping straight into the exit from above. I'd recommend dealing with it by means of a metal block surmounted with a fire object sealing the gap between the central two pillars.
Level 21: after that snag, this is also a good level. There is a lot of building, but the fact that you have to think about where to build and save all the lemmings easily makes up for it.
Level 22 is
really not my sort of level. To me it just doesn't fit the spirit of Lemmings -- it's a major part of the game that all the information you need to solve the level is visible, not tedious trial and error.