There's a bunch of stuff in Duke Nukem that they never used. The only thing we've found so far from Duke Nukem II is the following:
Here is some interesting remanents of a beta version found in nukem2.cmp.
This is a BETA COPY of Duke
Nukem II. Do not distribute.
This game is work in progress
and should not be viewed
by anyone outside Apogee!
Please report any illegal
use to Apogee Software at
Copied Art in Duke Nukem 2
As in Duke 1, Duke 2 borrowed a lot of graphics, most notable, again, from Turrican (source).
Duke Nukem 2 Idle Movie
A short movie plays that's a spoof of Lethal Weapon 1 and The Terminator if you leave Duke Nukem idle. Here are some shots from it.
Here are some random pictures from Duke Nukem 2 I didn't use elsewhere on this site: