This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
A very slick dark rubber grip pattern, sort of like the grip on a camera.
Source Sinisha
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
These dots are already worn for you, so you don’t have to.
Source Matt McDaniel
From a drawing in 'Az Osztrák-Magyar Monarchia irásban és képben', 1885.
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
This background pattern looks like bamboo to me. Feel free to download it for your website (for your blog perhaps?).
Source V. Hartikainen
This is the remix of "polka dot seamless pattern".The image depicts polka dot seamless pattern.
Source Yamachem
A version without colours blended together to give a different look.
Source Firkin
Original minus the background
Source Firkin
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Same classic 45-degree pattern, dark version.
Source Luke McDonald
A seamless background pattern with impressed gray dots.
Source V. Hartikainen
Prismatic Abstract Geometric Background 2
Source GDJ
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
Prismatic Snowflakes Pattern No Background
Source GDJ
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
A pattern formed from a photograph of a 16th century ceramic tile.
Source Firkin
From a drawing in 'Codogno e il suo territorio nella cronaca e nella storia'', Gio and Giarella Cairo, 1897.
Source Firkin