CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i
Source Firkin
Background pattern made in "Grunge-Like" style. Available in both SVG and JPG formats. Edit to your needs then click the download button.
Source V. Hartikainen
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Background Wall, Art Abstract, Star Well & CC0 texture.
Source Ractapopulous
Stefan is hard at work, this time with a funky pattern of squares.
Source Stefan Aleksić
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
From a drawing in 'Kingsdene', Maria Fetherstonehaugh, 1878.
Source Firkin
Geometric lines are always hot, and this pattern is no exception.
Source Listvetra
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A repeating background with a look of paper. I have added some changes to PatCreator. Now you can share your designs by submitting them to a new gallery section. Start by clicking Edit with PatCreator above.
Source V. Hartikainen
A brown metallic grid pattern layered on top of a dark fabric texture. It should look great when using as a tiled background on web pages, especially blogs.
Source V. Hartikainen
Black brick wall pattern. Brick your site up!
Source Alex Parker