The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
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
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Prismatic Snowflakes Pattern 3 No Background
Source GDJ
A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
ZeroCC tileabel stone granite texture, edited from pixabay. CC0
Source Sojan Janso
Remixed from a PNG that was uploaded to Pixabay by gingertea
Source Firkin
Prismatic Groovy Concentric Background 5 No Black
Source GDJ
This background texture resembles stone. It may be used as a background on web pages or on some of their html elements (header, borders, menu bar, etc.). Just modify it for your needs.
Source V. Hartikainen
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
Plywood Web Background background image for use in web design.
Source V. Hartikainen
Used a cherry by doctormo to make this seamless pattern
Source Firkin
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857
Source Firkin
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
Little x’es, noise and all the stuff you like. Dark like a Monday, with a hint of blue.
Source Tom McArdle
This is lovely, just the right amount of subtle noise, lines and textures.
Source Richard Tabor
A seamless green background texture. The image is distributed under a Creative Commons License (like all of the images here).
Source V. Hartikainen
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
You may use it as is, or modify it as you like.
Source V. Hartikainen
Prismatic Geometric Pattern Background No Black
Source GDJ
The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.
Source Firkin