Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
ZeroCC tileable mossy (lichen) stone texture, edited from pixabay. CC0
Source Sojan Janso
Sometimes you just need the simplest thing.
Source Fabricio
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
U.S.-based National Fire Protection Association standard fire diamond for flagging risks posed by hazardous materials. The red diamond has a number 0-4 depending on flammability. The blue diamond has a number 0-4 depending on health hazard. The yellow has a number 0-4 depending on reactivity. the white square has a special notice, e.g OX for oxidizer.
Source Firkin
Number 1 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Continuing the geometric trend, here is one more.
Source Mike Warner
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857
Source Firkin
Sounds like something from World of Warcraft. Has to be good.
Source Tony Kinard
Black brick wall pattern. Brick your site up!
Source Alex Parker
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Geometric lines are always hot, and this pattern is no exception.
Source Listvetra
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
This ons is quite old school looking. Retro, even. I like it.
Source Arno Declercq
A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
Colour version of the original pattern inspired by the front cover of 'Old and New Paris', Henry Edwards, 1894.
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ