$ sudo apt-get update
$ sudo apt-get install nexuiz-textures 

nexuiz-textures is installed in your system.

Make ensure the nexuiz-textures package were installed using the commands given below,

$ sudo dpkg-query -l | grep nexuiz-textures *

You will get with nexuiz-textures package name, version, architecture and description in a table

nexuiz-textures package basic information: