Over 600 variations of the gray textures (GRAY1, GRAY2, etc). These include 84 different layouts, with four colours of each (the standard gray, plus brown, green, and tan), plus variations with warning stripes and blue and red backgrounds.
In addition, several of the original gray textures have been slightly modified.
ID Software for the original textures (from Doom 1 and Doom 2)
Espi, whose awesome Suspended In Dusk .wad inspired several of the textures in this pack.