Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
A beautiful dark padded pattern, like an old classic sofa.
Source Chris Baldie
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
This is the remix of "Background pattern 115" uploaded by "Firkin".Thanks.
Source Yamachem
An abstract Background pattern of purple twisty patterns.
Source TikiGiki
You know I love paper patterns. Here is one from Stephen. Say thank you!
Source Stephen Gilbert
Used a cherry by doctormo to make this seamless pattern
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
Prismatic Abstract Geometric Background 4
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Zero CC plastic pattern texture, photographed and made by me. CC0 *Note, this texture was on the perfectly smooth surface of a plastic shovel scraper, not sure how to call it. Plz coment if you know what its called.
Source Sojan Janso
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
A free grid paper background pattern for using on web sites.
Source V. Hartikainen
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus