Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
The name is totally random, but hey, it sounds good.
Source Atle Mo
Remixed from a drawing in 'Some account of the Worshipful Company of Ironmongers', John Nicholl, 1866.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
A dark gray, sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Zero CC tileable dry grass texture, photographed and made by me. CC0
Source Sojan Janso
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
The image is a seamless pattern which is derived from a vine .Consequently, the vine got like dots via vectorization.The original vine is here:jp.pinterest.com/pin/500744052301410188/
Source Yamachem
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
A seamless web texture of "green stone".
Source V. Hartikainen
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
Detailed but still subtle and quite original. Lovely gray shades.
Source Kim Ruddock
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić