There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
Number five from the same submitter, makes my job easy.
Source Dima Shiper
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
Zero CC tileable Laminate wood texture, photographed and made by me. CC0
Source Sojan Janso
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
Stefan is hard at work, this time with a funky pattern of squares.
Source Stefan Aleksić
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
The image depicts a seamless pattern of a Japanese family crest called "chidori" in Japanese .A chidori in Japanese means a plover in English.
Source Yamachem
A background tile for web with abstract repeating texture of dark "stone wall".
Source V. Hartikainen
Textured Red Brown Plastic, Free Background Pattern. Although there's already enough plastic in our lives, let's bring it to the web too.)
Source V. Hartikainen
Tiny little flowers growing on your screen. Nice, huh?
Source Themes Tube
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
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
Background pattern originally a PNG drawn in Paint.net
Source Firkin
A seamless light gray paper texture with horizontal double lines.
Source V. Hartikainen
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
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
This is a hot one. Small, sharp and unique.
Source GraphicsWall
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Prismatic Hexagonalist Pattern No Background
Source GDJ
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
CC0 and seamless wellington boot pattern.
Source SliverKnight
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
Prismatic Triangular Background Design Mark II 5
Source GDJ