Prepared mostly as a raster in Paint.net and vectorised.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
The name is totally random, but hey, it sounds good.
Source Atle Mo
Prismatic Basic Pattern 2 No Background
Source GDJ
A dark pattern made out of 3×3 circles and a 1px shadow. This works well as a carbon texture or background.
Source Atle Mo
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
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 pattern of "sewn stripes" colored in light gray.
Source V. Hartikainen
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A free seamless background pattern for use on websites.
Source V. Hartikainen
One more sharp little tile for you. Subtle circles this time.
Source Blunia
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
Remixed from an image on Pixabay, the original having been uploaded by darkmoon1968.
Source Firkin
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A bit of scratched up grayness. Always good.
Source Dmitry
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Prismatic Groovy Concentric Background 5 No Black
Source GDJ
A free tileable background colored in off-white (antique white) color.
Source V. Hartikainen