Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
Formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
This is the remix of "Tileable Wave Pattern 2" uploaded by "Arvin61r58".Thanks.I added a wire-mesh fence seamless pattern as a lower layer.
Source Yamachem
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
A simple bump filter made upon request at irc #inkscape at freenode. Made a screen capture of the making here: https://youtu.be/TGAWYKVLxQw
Source Lazur URH
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
Prismatic Abstract Background Design
Source GDJ
ZeroCC tileabel stone granite texture, edited from pixabay. CC0
Source Sojan Janso
A seamless web texture with illustration of pale color stains on canvas.
Source V. Hartikainen
A repeating gloomy background image. This one consists of a pattern of black chains layered on top of a dark textured background.
Source V. Hartikainen
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A bit simplified version. Although it could be edited out to be simpler. Anyway, this time the tiling is converted to a pattern fill -which is using clipping for the tile's edges.
Source Lazur URH
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A free background tile with a pattern of pink bump dots. This background tile is sweet! Moreover, it's designed for use as website backgrounds.
Source V. Hartikainen
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
A seamless pattern formed from a modified version of rwwgub's tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida