Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
A beautiful dark wood pattern, superbly tiled.
Source Omar Alvarado
This is a seamless pattern of a woody texture.The original image is here:https://pixabay.com/ja/users/ClassicallyPrinted-1302233/
Source Yamachem
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
From a drawing in 'Picturesque New Guinea', J Lindt, 1887.
Source Firkin
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
A seamless pattern formed from a tile made from ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This one is amazing, truly original. Go use it!
Source Viahorizon
Feel free to use this seamless background texture as a background on a web site. It's colored in a light pink color and is seamlessly tile-able.
Source V. Hartikainen
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
The image depicts a shell seamless pattern.I used an OCAL clipart called "Shell" uploaded by "jgm104".Thanks.
Source Yamachem
To get the repeating unit, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
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
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
Dark blue concrete wall with some small dust spots.
Source Atle Mo
Luxury pattern, looking like it came right out of Paris.
Source Daniel Beaton
From an image on opengameart.org shared by rubberduck.
Source Firkin
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin