Even if I give you the DAT/LVLs for them, the fact is Windows Lemmings doesn't support special graphics levels. Even in the DOS version the special graphics levels' terrain are stored in a different format from normal graphics. The best I can give you is a BMP version of those graphics. I have no knowledge of how WinLemm stores terrain graphics and even if I do, it might not be possible to store a 960x160 bitmap as a terrain piece.
WinLemm indeed has the LVL files for the 4 special levels, but they just define the stats, entries and exists (not the actual "special" objects). There are even mini-screenshots for these levels, where you can just see the entry and exit. So my suspicion is, that these levels were treated "specially" on the Amiga version as well. Most probably the background image was not just stored as terrain tile, but it was loaded directly into the background mask.
Anyway, due to the enhancement of the SPR format used in WinLemm, I think it should be possible to store images that large - the question is however if WinLemm is able to read and process them or if it has some internal restrictions. Even if, one would need a converter to SPR format (which doesn't exist yet AFAIK), also the LVL file would have to be changed and last but not least you would have to find a way to force WinLemm to actually use the LVL file (which it doesn't). Not to mention WinLemm kinda sucks on fast computers (e.g. FF is unusable).
All in all I certainly agree that Lemmini would be the better choice - after all that's the reason why I did it