A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
Prismatic Groovy Concentric Background 4
Source GDJ
Mostly just mucked about with the colours and made one of the paths in the lead frame opaque. The glass remains transparent.
Source Firkin
Prismatic Abstract Background Design No Black
Source GDJ
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
The image depicts a Japanese Edo pattern called "kanoko or 鹿の子" meaning "fawn" which has a fur with small white spots.
Source Yamachem
A seamless background pattern with impressed gray dots.
Source V. Hartikainen
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
Prismatic Triangular Seamless Pattern III With Background
Source GDJ
It’s an egg, in the form of a pattern. This really is 2012.
Source Paul Phönixweiß
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
You guessed it – looks a bit like cloth.
Source Peax Webdesign
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein