This was formed by distorting an image of a background on Pixabay.
Source Firkin
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Prismatic Abstract Geometric Background derived from an image on Pixabay.
Source GDJ
Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
A free seamless background with pink spots.
Source V. Hartikainen
Sort of like the Photoshop transparent background, but better!
Source Alex Parker