Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
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
Zero CC tileable ground (#2) cracked, crackled texture, made by me. CC0
Source Sojan Janso
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
A free tileable background colored in off-white (antique white) color.
Source V. Hartikainen
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
This yellow background consists of a pattern of glossy gold buttons arranged in polka dot style on a seamless texture. Here's a pale yellow background pattern. Feel free to use it for your needs!
Source V. Hartikainen
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Number five from the same submitter, makes my job easy.
Source Dima Shiper
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
A very slick dark rubber grip pattern, sort of like the grip on a camera.
Source Sinisha
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
Not so subtle. These tileable wood patterns are very useful.
Source Elemis
The image is a remix of "edo pattern-samekomon".I changed the color of dots from black to white and added BG in light-yellow.
Source Yamachem
From a drawing in 'Cassell's Library of English Literature', Henry Morley, 1883.
Source Firkin