This was formed by distorting an image of a background on Pixabay.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
A comeback for you: the popular Escheresque, now in black.
Source Patten
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
Sharp but soft triangles in light shades of gray.
Source Pixeden
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Floral patterns might not be the hottest thing right now, but you never know when you need it!
Source Lauren
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
Vertical lines with a bumpy, yet crisp, feel to it.
Source Raasa
Prismatic Snowflakes Pattern No Background
Source GDJ
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
Submitted in a cream color, but you know how I like it.
Source Devin Holmes
A lot of people like the icon patterns, so here’s one for your restaurant blog.
Source Andrijana Jarnjak
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker