A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
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
This was formed by distorting an image of a background on Pixabay.
Source Firkin
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
Colourful background achieved with gradient fills.
Source Firkin
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
Prismatic Abstract Geometric Background 3
Source GDJ
A seamless pattern formed from a modified version of rwwgub's tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
This background pattern looks like bamboo to me. Feel free to download it for your website (for your blog perhaps?).
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Psychedelic Geometric Background No Black
Source GDJ
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
Prismatic Polka Dots 3 No Background
Source GDJ
With a name like this, it has to be hot. Diagonal lines in light shades.
Source Isaac
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Prismatic Polka Dots Mark II 2 No Background
Source GDJ