So, now that the NeoLemmix Introduction Pack is out of the way, I think it's time to say a bit more about ZZ Project. And the reason I'm posting that here is that, it's going to be a sequel to Doomsday Lemmings; but I feel it's too early to give it its own topic at this stage. I haven't decided yet if I'll simply call it "Doomsday Lemmings II" or give it a new name; so for the meantime I'll continue to refer to it as ZZ Project. (The "ZZ" is essentially a cryptic way of saying "Zombies 2", a reference to Doomsday Lemmings's codename of "Zombie Project")
So, what exactly is planned for this sequel? My current intention is to go for about 40 levels, probably over four ranks. Yes, that's quite a lot bigger - but there's a new feature to be used that make me feel that a pack similar in size to Doomsday Lemmings wouldn't be able to make enough use of them. You might've noticed I made reference in several places to a gimmick which exists in NeoLemmix V1.35n-C (actually, it existed for a couple of versions before that too) but hasn't been revealed yet. And yes, indeed, that gimmick is for use in this pack.
So, in addition to the Zombie lemmings you're familiar with from Doomsday Lemmings, there's another new type of lemming here - ghost lemmings! Ghost lemmings are quite different from zombies; the first and most obvious difference is that ghosts are not infectious. They also don't directly harm other lemmings - I say directly, because it isn't impossible for a scenario where they cause harm to exist; it's just not an inherent trait. Other lemmings will be scared of ghosts, and thus, if they get too close, they will turn to face away from the ghost. In this way, the ghost acts somewhat like a moving blocker, although with a slightly larger area of effect.
Ghost lemmings also can be assigned skills. These skills will have the full effect the skill normally would (with two exceptions due to a property of them I'm about to discuss); it should be noted that ghosts continue to deflect other lemmings while performing these skills, however. Another major difference from a regular lemming, however, is that ghosts do not interact with objects at all. They can walk straight past a trap; they cannot use an exit; they won't burn on contact with a fire object, and so on. This does mean that two skills have no use whatsoever when given to ghosts - Swimmer and Disarmer. This lack of interaction extends to the cases where interaction can exist with other lemmings - they will walk straight through blockers, and in the case of a level featuring both ghosts and zombies, they cannot be infected by zombies. Essentially, the only thing that they interact with is terrain; they remain unable to destroy steel, but they are not affected by one-way walls, and thus can destroy them while facing the wrong direction (or destroy one-way down arrows as bashers).
There are also two less significant gimmicks which I may end up using in this pack, one of which is already revealed (although not, as far as I know, been used yet). These are of a similar nature to each other, "Zombies on Death" and "Ghosts on Death". In these cases, a lemming that dies, instead of disappearing, becomes a zombie or a ghost respectively (this does not apply to lemmings that are already a zombie or a ghost when they die).
In terms of graphic sets, I don't plan to make any new ones - it'll just be using the Horror set (and I'm considering also using the Candy set as well, to give it a more halloween-y feel). I have added two extra terrain pieces to the Horror set, which will act as warning signs to let the player know when one of these "on death" effects is in play; the Zombie version can be seen in my current avatar (which also answers the question to anyone who was wondering what it might be). These extra pieces are already included in the Horror set in the latest NeoLemmix updates.
I haven't yet started on this pack beyond the planning stage, but the new gimmicks are fully implemented in NeoLemmix, as are the modifications to the Horror set. I don't plan to make corresponding additions to the Candy set, mostly because I'm not yet certain if I will use it or not. In the event that I do, the warning signs can always be implemented via VGASPECs.