From a drawing in 'Hyde Park from Domesday-Book to date', John Ashton, 1896.
Source Firkin
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Luxurious looking pattern (for a T-shirt maybe?) with a hint of green.
Source Simon Meek
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
A repeating background with wood/straw like texture.
Source V. Hartikainen
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
From an image on opengameart.org shared by rubberduck.
Source Firkin
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
Here's a dark background pattern that contains a steel grid pattern as a texture. Use it as a website background or for other purposes. It's free!
Source V. Hartikainen
Here's a tile-able wood background image for use in web design.
Source V. Hartikainen
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Background Wall, Art Abstract, Star Well & CC0 texture.
Source Ractapopulous
A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
A seamless background texture of old cardboard.
Source V. Hartikainen
Sometimes you just need the simplest thing.
Source Fabricio
A free seamless background texture that looks like a brown stone wall.
Source V. Hartikainen
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
One can never have too few rice paper patterns, so here is one more.
Source Atle Mo
Kaleidoscope Prismatic Abstract No Background
Source GDJ