Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
This background has abstract texture with some similarities to wood.
Source V. Hartikainen
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
Zero CC asphalt, pavement, texture, photographed and made by me. CC0 WARNING I FOUND A SEAM ON THIS TEXTURE
Source Sojan Janso
Prismatic Geometric Tessellation Pattern 3 No Background
Source GDJ
Seamless Background For Websites. It has a texture similar to cork-board.
Source V. Hartikainen
From a drawing in 'La Principauté de Liège et les Pays-Bas au XVIe siècle', Société des Bibliophiles Liégeois ,1887.
Source Firkin
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
Prismatic Geometric Pattern Background 2 No Black
Source GDJ