From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
Tile available in Inkscape using shift-alt-i on the selected rectangle
Source Firkin
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
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
Use shift+alt+i on the selected rectangle in Inkscape to get the tile this is based on
Source Firkin
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
An alternative colour scheme to the original seamless pattern.
Source Firkin
A seamless background texture of old cardboard.
Source V. Hartikainen
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
From a drawing in 'Picturesque New Guinea', J Lindt, 1887.
Source Firkin
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
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
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
I’m starting to think I have a concrete wall fetish.
Source Atle Mo
Prismatic Snowflakes Pattern 2 No Background
Source GDJ
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady