Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.
Source Firkin
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
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
Same as the black version, but now in shades of gray. Very subtle and fine grained.
Source Atle Mo
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Green Web Background, Seamless tile.
Source V. Hartikainen
Prismatic Groovy Concentric Background 4
Source GDJ
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
To get the repeating unit, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
Light gray paper pattern with small traces of fiber and some dust.
Source Atle Mo
Inspired by a drawing seen in 'City of Liverpool', James Picton, 1883.
Source Firkin
A new one called white wall, not by me this time.
Source Yuji Honzawa
Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
Heavily remixed from a drawing in 'Barbara Leybourne; a story of eighty years ago', Sarah Hamer, 1889.
Source Firkin
An abstract texture of black metal pipes (seamless).
Source V. Hartikainen