are these included on duke nukem 3d atomic, which i have from gog. they don't look anything like those i've seen on youtube?

obviously not

The version provided by GOG features original graphics only. However, you can use a free source port called eDuke32 to add better graphics if you like. You can even replace the enemies with 3D models instead of sprites. There are many threads in this forum about how to use eDuke32... basically if you just put eDuke32 into the folder you installed the game to, you can run the game through eDuke32 instead of DOSBox. Then you can use the options menu on eDuke32 to add new graphics if you want.