Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Just like your old suit, all striped and smooth.
Source Alex Berkowitz
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
An abstract web texture of a polished blue stone (or does it look more like ice).
Source V. Hartikainen
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
Prismatic Abstract Line Art Pattern Background
Source GDJ
8 by 8 pixels, and just what the title says.
Source pixilated
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Prismatic Basic Pattern 2 No Background
Source GDJ
emixed from a JPG that was uploaded to Pixabay by Kyotime
Source Firkin
This seamless light brown background texture resembles a wallpaper with vertical stripes. One way to use it is as a tiled background on web sites.
Source V. Hartikainen
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
Seamless Background For Websites. It has a texture similar to cork-board.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Tiny little fibers making a soft and sweet look.
Source Badhon Ebrahim
Washi (和紙?) is a type of paper made in Japan. Here’s the pattern for you!
Source Carolynne
Prismatic Snowflakes Pattern 2 No Background
Source GDJ
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin