It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
A seamless pattern formed from cross 4. To get the original tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A re-make of the Gradient Squares pattern.
Source Dimitar Karaytchev
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
This ons is quite old school looking. Retro, even. I like it.
Source Arno Declercq
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
Otis Ray Redding was an American soul singer-songwriter, record producer, arranger, and talent scout. So you know.
Source Thomas Myrman
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
Seamless Light Background Texture.
Source V. Hartikainen