Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
A repeating background of beige (or is it more vanilla yellow) textured stripes. One more background with stripes.
Source V. Hartikainen
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
Looks like an old wall. I guess that’s it then?
Source Viahorizon
From a drawing in 'Royal Ramsgate', James Simson, 1897.
Source Firkin
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
A pattern drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
From a drawing in 'A Rolling Stone. A tale of wrongs and revenge', John Hartley, 1878.
Source Firkin
This is a seamless pattern which is derived from a flower petal image.
Source Yamachem
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
Remixed from a vector adapted from a jpg on Pixabay. The tile this is constructed from can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin