A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
A bit strange this one, but nice at the same time.
Source Diogo Silva
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Remixed from a drawing in 'Analecta Eboracensia', Thomas Widdrington, 1897.
Source Firkin
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
This makes me wanna shoot some pool! Sweet green pool table pattern.
Source Caveman
Prismatic Snowflakes Pattern 3 No Background
Source GDJ
Remixed from an image on Pixabay, the original having been uploaded by darkmoon1968.
Source Firkin
A floral background formed from numerous clones of flower 117.
Source Firkin
Coming in at 666x666px, this is an evil big pattern, but nice and soft at the same time.
Source Atle Mo
A seamless marble-like texture colored in light blue.
Source V. Hartikainen
Prismatic Geometric Pattern Background 2 No Black
Source GDJ
I skipped number 3, because it wasn’t all that great. Sorry.
Source Dima Shiper
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
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
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A re-make of the Gradient Squares pattern.
Source Dimitar Karaytchev