An abstract Background pattern of purple twisty patterns.
Source TikiGiki
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
From an image on opengameart.org shared by rubberduck.
Source Firkin
A seamless pattern made from the gold Penrose triangle by GDJ and the two remixes
Source Firkin
This ons is quite old school looking. Retro, even. I like it.
Source Arno Declercq
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Prismatic Geometric Tessellation Pattern 3 No Background
Source GDJ
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
The image a seamless pattern derived from a weed which I can't identify.The original weed image is from here:https://jp.pinterest.com/pin/500744052301423641/
Source Yamachem
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Bumps, highlight and shadows – all good things.
Source Badhon Ebrahim