I'm in agreement about the triggered decorations. While they could potentially be neat, they are misleading and don't really add anything to the gameplay.
Radiation and slowfreeze levels are admittedly difficult to make without just being obnoxious. Still, I think I've helped to prove that it can be done in Casualemmings. I'm not so sure I'd like to see them just go away.
The disarmer is kind of in the same boat. There are often other ways to get around traps, but that would require giving out more skills to circumvent them, skills that could be used elsewhere to break something. Making a level where the disarmer stands out is a matter of managing the disarmer's location compared to the rest of the lemmings. I think that 'Fixed Ascent' in namida's Introduction Pack does this well.

Saturday evenings tend to be open for me, so that would work out nicely.

Version 1.2 is now out!

This forum is frequented by experts at Lemmings, who love to make really hard levels.
I am not one of them, and cannot conquer some of their devilish creations.
Perhaps you're in my boat? Or maybe you're just like Lemmings but are new to NeoLemmix?
In that case, this pack could be the one for you!

Featuring 100 levels across five ratings, this pack contains many easier levels for the casual player to enjoy, but also a few tough ones as well.
(Yeah, I know I said that about my first pack but bear with me here )

Calm - 30 levels
A relaxing romp that introduces many of the new skills and objects in NeoLemmix, and doesn't have too many difficult challenges. Puzzles are fairly simple, and many levels give you significantly more than you need to win.

Perky - 25 levels
This rating introduces a few more NeoLemmix mechanics. Puzzles are a bit tougher. Levels still often give you more than you need, but the wiggle room is a bit less than in Calm.

Twitchy - 20 levels
The puzzles start getting hard here. You'll have to use skills in some odd ways and manage your Lemmings carefully so they don't meet with terrible fates. Though many of them will be doomed anyway... Still, expect wiggle room on at least a few levels.

Hyper - 15 levels
If you're looking for some puzzles that are a real challenge, you may just find them here. Don't expect anything Spiky or Sharp (except perhaps a few traps here and there, ho ho), but these aren't a cakewalk either. Wiggle room is sparse, but still existent on some levels.

- 10 levels
QUARANTINE. NO ENTRY WITHOUT AUTHORIZATION

Oh, and oftentimes the last few levels in a rating are harder than the starting levels in the next rating. My reasoning is as follows:
https://www.youtube.com/watch?v=i3GzZtx2xes

As for talismans, we've got those too! 12 talisman challenges for you to try out. 2 of them don't tell you directly what to do either, but rather present a riddle...
Of course, if that isn't your thing, you can just check here to see what those riddles are asking.

Download the custom music here: https://www.dropbox.com/s/gmbtedsac54nx27/CasualemmingsMusic.zip?dl=1
If upgrading from version 1.1, you need only download this new music: https://www.dropbox.com/s/u3khzg6ux6kdyeu/CasualemmingsMusic2.zip?dl=1
The level pack is attached to the post.

Thursday is my busiest night so I won't be able to join in. Have fun though!

One thing I've tried is to just offset all the pickups by one pixel each. It's clear that there's more than one there that way, and it honestly doesn't take all that much space. Still, your idea could make it very concise and immediately clear.
Admittedly, somebody could get rather rude with this by stacking pickups of different types behind each other so you can't clearly see which is which. Even clear physics mode wouldn't immediately reveal such treachery...

The Pit of 100 trials in Thousand Year Door can be totally cheesed with a Danger Mario setup. If you never improve your max HP and then use Chet Rippo to decrease it down to 5, you will always be in Danger so you can equip tons of Danger Rush badges and increase your attack power by a huge amount at all times. You can only do this once you reach chapter 7 and you have to farm the arcade a whole lot to get all those badges, but destroying Magnus Von Grapple 2.0 with one Power Bounce is super satisfying. If you equip all the other badges that boost defense and evasion when you're in Danger then many enemies can't hurt you either. The aforementioned Magnus Von Grapple 2.0's audience cannon then becomes completely hilarious. *whiff whiff whiff clink whiff whiff clink clink etc*

I tend to shy away from hard games, but I know I've completed Mario Sunshine 100% at one point... I have beaten Pokemon Puzzle Challenge on Intense with no continues a few times. Does that count for anything?

I've started playing through this and jumping around the difficulty ratings. It's been pretty fun so far, though the difficulty does fluctuate quite a bit.
Troll levels just don't work in NeoLemmix, as I learned the hard way. Pretty much anyone is going to press the clear physics button and then all of the trolling is revealed.
I do like how you put the traps behind the creatures. It just looks neat, even though there are some who I know will hate this. "The Black Widow" was pretty fun to see how the traps were stacked up like that.
I do believe I've found some backroutes though. "Painful Parkour" seemed a bit too easy because I found a way to basically ignore the bottom half of the level, and "Luring Lemmings into mousetraps" can be done by just using a digger near the start and cranking the release rate. I also feel like "Lemming epigenetics" and "Shock absorber" aren't different enough. The reduction in skills for the harder level doesn't really change anything.
These are just some things I've noticed up to this point. Overall it's looking good though!