This is an awesome set of High Resolution textures for the Quake 2 source ports, gathered and sorted from the many of the different packs. This article and screenshots cover the performance of Quake II Evolved with the High Resolution textures pack for Quake 2.
Ensure that you have Quake II Evolved installed and configured as described in above article. Ensure that the 'Texture quality' is set to 'Max' in video options.
Unpack the textures archive to the 'baseq2' subfolder of original game (this was 'E:\games\Quake II\baseq2' in my case).