A repeating background with dark brown stone-like texture and abstract pattern that looks like tree trunks.
Source V. Hartikainen
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!
Source Dertig Media
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Zero CC tileable hard cover green book, scanned and made by me. CC0
Source Sojan Janso
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
Tweed is back in style – you heard it here first. Also, the @2X version here is great!
Source Simon Leo
Inspired by an image that was uploaded to Pixabay by geralt
Source Firkin
A re-make of the Gradient Squares pattern.
Source Dimitar Karaytchev
Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom
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
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers