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
Zero CC tileable wood texture, made by me procedurally in Neo Texture Edit.
Source Sojan Janso
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
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
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
A grayscale fabric pattern with vertical lines of stitch holes.
Source V. Hartikainen
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A beautiful dark wood pattern, superbly tiled.
Source Omar Alvarado
Sounds like something from World of Warcraft. Has to be good.
Source Tony Kinard
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
An aged paper background tile with smeared and pressed text.
Source V. Hartikainen
I love the movie Pineapple Express, and I’m also liking this Pineapple right here.
Source Audee Mirza
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
From a drawing of the coat of arms of the Ottoman Empire on Wikimedia.
Source Firkin