ZeroCC tileable moss texture, photographed and made by me. CC0
Source Sojan Janso
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Background formed from the original with an emboss effect
Source GDJ
Retro Circles Background 7 No Black
Source GDJ
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
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
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin