That would be an awesome feature! 
In traditional Lemmix I only added all new Lemmini styles into the ini, so it wasn't a big problem there, but in the NeoLemmix editor it seems a bit tricky to copy all my gathered tilesets to SuperLemmini and other systems (I had lots of trouble with Christmas(how I named it) beeing now xmas; the different folders you have to create and manage and so on).
The idea (if I got it correctly) of having one style folder with the basic sets for all and simply just copy all the new tilesets for NeoLemmix, Lemmini....  in the dedicated folder without changing the ini every time would be a blessing 
I stay with Lemmix for the rest of my pack (112/150 btw  ), but after that is done: With this feature it would be much easier to get into the NeoLemmix editor (together with the tutorial you are planning to do maybe) 

I think Custom Tilesets add a lot of variety to a pack. More different architectures and more different ways to create beautiful looking levels (especially if the custom ones have a specific theme which you can work on). Also the different terrain pieces could inspire new tricks. The official tilesets will always be a standard, but in my opinion the custom ones are the way to go to spice things up and to create more different looking landscapes.

And in Lemmini it's very easy to add new custom tilesets (just copy the folder in "styles" and you're good to go). This and the fact that I prefer the "new" Lemmini physics and Lemming selection mechanics (apart from the basher glitch) over the oldschool DOS physics and mechanics, are the main points why I create my first pack for Lemmini.

GOT IT!    My solution is Messy as hell, not without misplays and 100% could have saved more (76% is really pathetic lost ~ 10 Lems just through misplays), but I got through! Replay attached played in NeoLemmix.

(The 100% one must really be a masterpiece of precisicion and planning)

Huge respect for that Monster you have created, Nepster 

Solved two of them (100%). Replays attached! (You can probably guess which one needs some VERY deep thinking. My very first ALPHA attemt is in there, too)

Some thoughts:

Super Starship:

On the same level:

Criteria fulfilled!:

Yes, but I have no clue how to put them together for an Lemmini tileset (or how to extract them into the right format). It usually uses gif files of the terrain and objects and binds them together in a text document.

I finally downloaded this game today, my solutions are attached!

I noticed in Outbreak 5: "Cursed Affliction" that zombies are contagious even through 3 pixel wide walls when I dug two holes next to each other at first. But it's maybe understandable.
Outbreak 2: "Haunted Pier", Plague 3: "Take One For The Team" and Plague 5: "Terror Cove" were pretty nice levels! Apocalypse 2: "Infection Bypass" was my least favourite one, the execution was somewhat frustrating there.
I don't know why the exit didn't open in Apocalypse 5: "One Last Lemming" (maybe you're supposed to be doomed at the end of the game ) and other Apocalypse levels I suspect backrouting and neglecting to use the gimmick.
What does the text say in Plague 1: "Cycle Of Undeath", by the way?

Apocalypse 5 can be beaten. Hint:
I've got a nice minimal frustrating solution with a spare blocker and more lemmings saved as you needed for Apocalypse 2 just check my channel if my uploads reach that level.

Congratulations Crane for winning the contest!!!

I voted Crane's Precarious Construction (Part 2) and IchoTolot's Shadowrun in the first round and IchoTolot's Shadowrun in the second round. These two levels I found the most attractive looking, and I found Shadowrun alongside keiya's Careless Oasis to work as the authors wanted them to work. I'm really wondering though that Crane's level actually managed to win after that IchoTolot's level gained 6 votes from 6 voters in the first round against Crane's 4 votes from 6 voters, and the final resulted in Crane's 4-3 victory. Did someone change his/her mind in the middle of the contest? Anyway, a great rise for the underdog contender to be the final winner after all, Crane!

IchoTolot, this was the first level I ever played from you and I can say that I am really anticipating your upcoming levelpack, this was fantastic. Crane, same to you, I've waited for your levelpack for few years already, maybe you're still working with it hopefully? Anyway, good job all the contenders, I enjoyed a lot playing everyone's levels after getting to used to NeoLemmix also.

Thx for the nice comment! I try to keep up the standard and maybe even improve my creating skills in the progress (esspecially the decorating side, if the terrain maximum allows it), to make the final pack as good as it can get!
I have a little secret about the second voting round: I myself voted for Crane's level