Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
Imagine you zoomed in 1000X on some fabric. But then it turned out to be a skeleton!
Source Angelica
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Used the 6th circle pattern designed by Viscious-Speed to create a print that can be used for card making or scrapbooking. Save as a PDF file for the best printing option.
Source Lovinglf
Alternative colour scheme for the original floral pattern.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Abstract Background Design No Black
Source GDJ
Very simple, very blu(e). Subtle and nice.
Source Seb Jachec
Prismatic Groovy Concentric Background 5 No Black
Source GDJ
A nice and simple white rotated tile pattern.
Source Another One
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
A seamless stone-like background for blogs or any other type of websites.
Source V. Hartikainen
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo