It's not authorized yet, but here's a link in anycase:
http://www.moddb.com/mods/imagination-worl...v2-to-v21-patch
It's about 40mb and includes these things:
-Art files integrated into main Duke3d.grp to enable mod support
-Fixed some Government Trooper art issues and enabled injured AI
-Alternate map set without skybox support for people with skybox crashes
-Added Magnum to some more earlier levels
The crash issues aren't something I can really look into since most of the time the information it gives is enigmatic at best. The old snapshot and a newer one are both included; the newer one took MUCH longer to load and had worse performance, but it didn't crash on me after playing a few levels.
Once you install the patch, delete all the art files in the directory yourself or run the included bat file.