Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
Zero CC tileable brick texture, photographed and made by me. CC0
Source Sojan Janso
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Zero CC tileable ground (#2) cracked, crackled texture, made by me. CC0
Source Sojan Janso
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Retro Circles Background 5 No Black
Source GDJ
Seamless pattern the basic tile for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
Zero CC tileable hard cover cells, skin like, book texture. 4K, Scanned and made by me CC0
Source Sojan Janso
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Orange-red pattern for tiled backgrounds.
Source V. Hartikainen
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
Remixed from a drawing in 'Incidents on a Journey through Nubia to Darfoor', F. Ensor, 1891.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS
Pixel by pixel, sharp and clean. Very light pattern with clear lines.
Source M.Ashok
The image depicts a seamless pattern which was made using stripe-like things including borders.I used OCAL cliparts called "Blue Greek Key With Lines Border" uploaded by "GR8DAN" and "daisy border" uploaded by "johnny_automatic".Thanks.
Source Yamachem
Prismatic Abstract Geometric Background 4
Source GDJ
Prismatic Abstract Geometric Background 3
Source GDJ
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow