I'm beginning to see the light. I find myself looking for wrong ways to clear levels, just because they're wrong. They're not necessarily shorter or use fewer skills than the intended solutions, but they're so much wronger! I can't help myself!

Uh oh, it happened again! And it was my last of the 120, too!
Nice pictures! They certainly look like unintended solutions.
If you're looking for more 'wrong ways to clear levels, just because they're wrong', you could try some of the Original Lemmings Levels. I remember that Taxing 10 and Mayhem 25 had some clear backroutes, and that there were ceiling routes for Mayhem levels 7 and 17. There might be more though, so good luck in your searches!
Don't forget the old standby, the most hilariously obvious backroute in Lemmings history, Egypt 6!
All in favour of Guy's user-title becoming "Icky backroutist", raise your hand.

Anyway, keep 'em coming - this is particularly interesting to me, because until I came here, I was completely unaware of the concept of backrouting. Accordingly, I love seeing these.
Well, there were those Lemmings Revolution levels I did a while back...
12-7: The Long And Winding Road

11-9: Goonies

8-8: Take Her to Warp Speed, Captain!

I'm especially proud of that last one. The extended bridge is such a classic!
A classic from Original Lemmings....

Wow! That Egypt 6 backroute is just incredible.

Speaking of Lemmings Revolution, there are I think two backroutes in the 'Scale that wall' level. One which involves a lemming heading left to hit the switch (discovered by mobius around
here), and another which uses the elongated bridge trick to cross the large gap towards the switch. I can't upload images, so let's see if you can find them yourself.
A classic from Original Lemmings.... 

That level has all kinds of backroute opportunities. It's a good candidate for direct drop, too, if you're into that sort of thing...
This thread showcases one of my favorite things about Lemmings: There's almost always multiple ways to get things done. Sometimes it's fun to find all of the different ways you can go. Here are some of my favorite backroutes/alternate solutions.
Lemmings and ONML:
- The outside routes to Taxing 4 and Taxing 27
- The ceiling route to Crazy 19
- The floor route to Havoc 4
Lemmings 2:
- Stomp through the left wall at the start of Sports 5
- Going left and down from the start on Shadow 8 (using bashers and bazookas)
- The route depicted on The Lemmings Encyclopedia for Beach 2
Lemmings Revolution:
- Build over the first teleport in "Under and Up"
- Build left from the start in "Time is of the essence!"
- Head left from the start in "Watch out! Evil about!"
There are dozens more, but you get the idea.