I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
Might not be super subtle, but quite original in its form.
Source Alex Smith
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
Floral patterns will never go out of style, so enjoy this one.
Source Lasma
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
An alternative colour scheme for the original seamless texture formed from an image on Pixabay.
Source Firkin
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
Found on the ground in french cafe in kunming, Yunnan, china
Source Rejon
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
This could be a hippy vintage wallpaper.
Source Tileable Patterns