Non-seamless pattern drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
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
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
Number five from the same submitter, makes my job easy.
Source Dima Shiper
This was formed by distorting an image of a background on Pixabay.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Neat little photography icon pattern.
Source Hossam Elbialy
Remixed from a JPG that was uploaded to Pixabay by susanlu4esm
Source Firkin
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
The original enhanced with some gradients.
Source Firkin
Like the name suggests, this background image consists of a pattern of dark bricks. It may be an option for you, if you are looking for something that looks like a brick wall for use as a background on web pages. It's not a masterpiece, but looks pretty nice when is tiled.
Source V. Hartikainen
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ