Zero CC tileable hard cover red book, scanned and made by me. CC0
Source Sojan Janso
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
Like the name suggests, this background image consists of a pattern of dark bricks. It may be an option for you, if you are looking for something that looks like a brick wall for use as a background on web pages. It's not a masterpiece, but looks pretty nice when is tiled.
Source V. Hartikainen
Prismatic Groovy Concentric Background 5
Source GDJ
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
You may use it as is, or modify it as you like.
Source V. Hartikainen
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
Prismatic Polka Dots 3 No Background
Source GDJ
This ladies and gentlemen, is texturetastic! Love it.
Source Adam Pickering
From a drawing in 'Kingsdene', Maria Fetherstonehaugh, 1878.
Source Firkin