Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
This makes me wanna shoot some pool! Sweet green pool table pattern.
Source Caveman
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
Prismatic Curved Diamond Pattern 4 No Background
Source GDJ
Classic vertical lines, in all its subtlety.
Source Cody L
More in the paper realm, this time with fibers.
Source Jorge Fuentes
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
No, not the band but the pattern. Simple squares in gray tones, of course.
Source Atle Mo
Remixed from a drawing in 'Incidents on a Journey through Nubia to Darfoor', F. Ensor, 1891.
Source Firkin
A bit strange this one, but nice at the same time.
Source Diogo Silva
"Beige Stone", Tileable Texture.
Source V. Hartikainen
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
A nice and simple gray stucco material. Great on its own, or as a base for a new pattern.
Source Bartosz Kaszubowski
Prismatic Groovy Concentric Background 5
Source GDJ