A seamless pattern made from the gold Penrose triangle by GDJ and the two remixes
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Neat little photography icon pattern.
Source Hossam Elbialy
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
Sounds like something from World of Warcraft. Has to be good.
Source Tony Kinard
A repeating background of beige (or is it more vanilla yellow) textured stripes. One more background with stripes.
Source V. Hartikainen
From an image on opengameart.org shared by rubberduck.
Source Firkin
Paper model of a tetrahedron. Modelo de papel de um tetraedro.
Source laobc
Prismatic Curved Diamond Pattern 2 No Background
Source GDJ
Derived from a drawing in 'Historiske Afhandlinger', Adolf Jorgensen, 1898.
Source Firkin
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
I love the movie Pineapple Express, and I’m also liking this Pineapple right here.
Source Audee Mirza
A new one called white wall, not by me this time.
Source Yuji Honzawa
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
A seamless pale yellow paper background with a pattern of animal tracks.
Source V. Hartikainen
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett