Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
This one has rusty dark brown texture.
Source V. Hartikainen
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
CC0 and seamless wellington boot pattern.
Source SliverKnight
On a large canvas you can see it tiling, but used on smaller areas, it’s beautiful.
Source Paul Phönixweiß
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Abstract Tiled Background Extended 11
Source GDJ
A repeating background of beige (or is it more vanilla yellow) textured stripes. One more background with stripes.
Source V. Hartikainen
The perfect pattern for all your blogs about type, or type-related matters.
Source Atle Mo
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
There are many carbon patterns, but this one is tiny.
Source Designova
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen
Black & white version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Inspired by the B&O Play, I had to make this pattern.
Source Atle Mo
Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
There are many carbon patterns, but this one is tiny.
Source Designova
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
A repeating graphic with ancient pattern. I came up with this name/title at last minute, so you may find that there is very little of ancientness in this pattern after all.
Source V. Hartikainen
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
A seamless marble-like texture colored in light blue.
Source V. Hartikainen
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin