A free seamless background texture of "timber wall" (colored in dark brown).
Source V. Hartikainen
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
The image depicts a seamless pattern of a snow crystal.I referred to a book called ”sekka-zusetsu” or "雪華図説" which means an illustrated explanation about snow crystals.This book was published in 1832 (天保3年) or Edo period.For more about "雪華図説",see here:dl.ndl.go.jp/info:ndljp/pid/2536975
Source Yamachem
If you’re sick of the fancy 3D, grunge and noisy patterns, take a look at this flat 2D brick wall.
Source Listvetra
A free green background pattern with a pattern of rhombuses on a seamless texture. Feel free to use it as a tiled background image on your web site.
Source V. Hartikainen
A free seamless background with pink spots.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 4 No Background
Source GDJ
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
Orange-red pattern for tiled backgrounds.
Source V. Hartikainen
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
Remixed from an image on Pixabay, the original having been uploaded by darkmoon1968.
Source Firkin
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin