Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This is lovely, just the right amount of subtle noise, lines and textures.
Source Richard Tabor
This one needs to be used in small areas; you can see it repeat.
Source Luca
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
We have some linen patterns here, but none that are stressed. Until now.
Source Jordan Pittman
A seamless background texture of old cardboard.
Source V. Hartikainen
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
This yellow background consists of a pattern of glossy gold buttons arranged in polka dot style on a seamless texture. Here's a pale yellow background pattern. Feel free to use it for your needs!
Source V. Hartikainen
Number five from the same submitter, makes my job easy.
Source Dima Shiper
Prismatic Abstract Geometric Background 3
Source GDJ
You may use it as is, or modify it as you like.
Source V. Hartikainen
I skipped number 3, because it wasn’t all that great. Sorry.
Source Dima Shiper
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
A seamless striped fabric-like texture colored in a dark reddish brown color.
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ