A seamless striped fabric-like texture colored in a dark reddish brown color.
Source V. Hartikainen
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
Zero CC tileable moss or lichen covered stone texture, edited from pixabay. CC0
Source Sojan Janso
A dark gray, sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Alternative colour scheme for the original floral pattern.
Source Firkin
This makes me wanna shoot some pool! Sweet green pool table pattern.
Source Caveman
This one is amazing, truly original. Go use it!
Source Viahorizon
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
Prismatic Hypnotic Pattern No Background
Source GDJ
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
This seamless pattern consists of a blue grid on a yellow background.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective