A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
A nice and simple white rotated tile pattern.
Source Another One
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
This is sort of fresh, but still feels a bit old school.
Source Martuchox
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
This ons is quite old school looking. Retro, even. I like it.
Source Arno Declercq
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
Sort of like the back of a wooden board. Light, subtle, and stylish, just the way we like it!
Source Nikolalek
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A version without colours blended together to give a different look.
Source Firkin