A free seamless background texture of "timber wall" (colored in dark brown).
Source V. Hartikainen
A repeating gloomy background image. This one consists of a pattern of black chains layered on top of a dark textured background.
Source V. Hartikainen
Prismatic Basic Pattern 2 No Background
Source GDJ
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Zero CC tileable yellow craft paper; scanned and made by me. CC0
Source Sojan Janso
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
An attempt for cleaning up the original image in a few steps.
Source Lazur URH
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
A background pattern with blue on white vertical stripes.
Source V. Hartikainen
A seamless paper background colored in pale yellow.
Source V. Hartikainen