Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
From a drawing in 'An Old Maid's Love. A Dutch tale told in English', Maarten Maartens, 1891.
Source Firkin
Sharp pixel pattern, just like the good old days.
Source Paridhi
Sometimes you just need the simplest thing.
Source Fabricio
Psychedelic Geometric Background No Black
Source GDJ
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
Colour version of the original pattern.
Source Firkin
This is a seamless pattern of regular hexagon which has a honeycomb structure.
Source Yamachem
We have some linen patterns here, but none that are stressed. Until now.
Source Jordan Pittman
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Green Background Pattern
Source V. Hartikainen
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
This ladies and gentlemen, is texturetastic! Love it.
Source Adam Pickering
Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo