I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
Prismatic Triangular Background Design Mark II 5
Source GDJ
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Sounds like something from World of Warcraft. Has to be good.
Source Tony Kinard
Psychedelic Geometric Background 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 stone-like background for blogs or any other type of websites.
Source V. Hartikainen
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
This one is amazing, truly original. Go use it!
Source Viahorizon
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
White circles connecting on a light gray background.
Source Mark Collins
From a drawing in 'Friend or Fortune? The story of a strange year', Robert Overton, 1897.
Source Firkin
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec