Here is another pack for Retrolemmini
Nessy's Lemmings Migration: extract to the resources/levels folder
requires some new styles: extract to resources/styles folder
music: extract to the resources/music folder
replays: extract to the resources/replays folder
sound: 1 style (machine) added the trap sound to the sound folder. extract to the resources/sound folder
mod edit: The pack download has been setup so that you just need to extract to your RetroLemmini directory. Everything will fall into place.