Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A pale yellow background pattern with vertical stripes. The stripes are partially faded. I think this background image turned out pretty well, especially those faded stripes.
Source V. Hartikainen
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 2
Source GDJ
This background pattern contains a texture of yellow wood planks. I think it looks quite original.
Source V. Hartikainen
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
The tile can be had by using shift+alt+i on the selected rectangle in Inkscape
Source Firkin
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
This background pattern contains a seamless texture of bark. It's not very realistic, but I think it looks quite nice.
Source V. Hartikainen
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
From a drawing in 'Picturesque New Guinea', J Lindt, 1887.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A textured orange background pattern with vertical stripes.
Source V. Hartikainen
Coming in at 666x666px, this is an evil big pattern, but nice and soft at the same time.
Source Atle Mo
A lovely light gray pattern with stripes and a dash of noise.
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
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett