CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Textured Red Brown Plastic, Free Background Pattern. Although there's already enough plastic in our lives, let's bring it to the web too.)
Source V. Hartikainen
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
A seamless background tile of aged paper with shabby look.
Source V. Hartikainen
One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A bit of scratched up grayness. Always good.
Source Dmitry
A seamless textured paper for backgrounds. Colored in pale orange hues.
Source V. Hartikainen
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
Alternative colour scheme to the original.
Source Firkin
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A light brushed aluminum pattern for your pleasure.
Source Tim Ward
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
A seamless tessellation pattern. To get the tile this is formed from, select the pattern in Inkscape and use shift+alt+i.
Source Firkin