A comeback for you: the popular Escheresque, now in black.
Source Patten
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
A version without colours blended together to give a different look.
Source Firkin
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
One can never have too few rice paper patterns, so here is one more.
Source Atle Mo
Here's a brown background pattern with subtle stripes. I hope you'll like the color. If not, feel free to change it using an image editor, if you know how of course. Personally, I'm using GIMP to create these backgrounds.
Source V. Hartikainen
A simple bump filter made upon request at irc #inkscape at freenode. Made a screen capture of the making here: https://youtu.be/TGAWYKVLxQw
Source Lazur URH
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Remixed from a raster on Pixabay, that was uploaded by ArtsyBee.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A gray background pattern with a texture of textile. Suits perfectly for web design.
Source V. Hartikainen
Prismatic Triangular Background Design Mark II 5
Source GDJ
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Seamless Background For Websites. It has a texture similar to cork-board.
Source V. Hartikainen
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
The Grid. A digital frontier. I tried to picture clusters of information as they traveled through the computer.
Source Haris Šumić