A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A seamless background pattern of dark brown wood planks.
Source V. Hartikainen
You know I’m a sucker for these. Well-crafted paper pattern.
Source Mihaela Hinayon
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
From a drawing in 'Handbook of the excursions proposed to be made by the Lincoln Diocesan Architectural Society, on the 27th and 28th of May, 1857', Edward Trollope, 1857.
Source Firkin
A seamless pattern of leopard skin. It should look nice as a background element on web pages.
Source V. Hartikainen
Remixed from a drawing in 'Incidents on a Journey through Nubia to Darfoor', F. Ensor, 1891.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Groovy Concentric Background No Black
Source GDJ
A comeback for you: the popular Escheresque, now in black.
Source Patten
ZeroCC tileable beechwood wood texture, generated in Neo Texture Edit by me. CC0
Source Sojan Janso
It’s like Shine Dotted’s sister, only rotated 45 degrees.
Source mediumidee
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
A repeating background with wood/straw like texture.
Source V. Hartikainen