A comeback for you: the popular Escheresque, now in black.
Source Patten
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
Remixed from a drawing in 'A Girl in Ten Thousand', Elizabeth Meade, 1896.
Source Firkin
Remixed from a drawing in 'Canadian forest industries July-December', 1915
Source Firkin
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
A seamless pattern created from a square tile. To get the tile, select the pattern in Inkscape and use shift+alt+i.
Source Firkin
It’s like Shine Dotted’s sister, only rotated 45 degrees.
Source mediumidee
Zero CC tileable grass texture, photographed and made by me. CC0
Source Sojan Janso
A free seamless background with pink spots.
Source V. Hartikainen
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
A nice and simple white rotated tile pattern.
Source Another One
Prismatic Abstract Background Design No Black
Source GDJ
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