Yeah, I've got suggestion 😉 Forget about playing DN3D in DosBox. Visit THIS SITE, download and install high resolution pack and kick some high resolution aliens' asses. 😀

Or if, like me, you prefer to play the game with original graphics then just get this:

http://jonof.edgenetwork.org/index.php?p=jfduke3d

Or if you don't mind messing around a little and want to get the "true" Duke3D working then try this:

http://buildxp.deathmask.net/

Thanks for the suggestions. I'll try them.