A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
From a drawing in 'Handbook of the excursions proposed to be made by the Lincoln Diocesan Architectural Society, on the 27th and 28th of May, 1857', Edward Trollope, 1857.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
A bit strange this one, but nice at the same time.
Source Diogo Silva
Turn your site into a dragon with this great scale pattern.
Source Alex Parker
A repeating background of thick textured paper. Actually, it turned out to look like something between a paper and fabric.
Source V. Hartikainen
You were craving more leather, so I whipped this up by scanning a leather jacket.
Source Atle Mo
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin