This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
This is a seamless pattern which is derived from a flower petal image.
Source Yamachem
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Background pattern made in "Grunge-Like" style. Available in both SVG and JPG formats. Edit to your needs then click the download button.
Source V. Hartikainen
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Light and tiny, just the way you like it.
Source Rohit Arun Rao
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Dark blue concrete wall with some small dust spots.
Source Atle Mo
Prismatic Geometric Pattern Background
Source GDJ
A background pattern with wavy green vertical stripes. This one has green stripes on a white background. Download if you like it.
Source V. Hartikainen
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Feel free to use this seamless background texture as a background on a web site. It's colored in a light pink color and is seamlessly tile-able.
Source V. Hartikainen
A seamless texture of an abstract wall colored in shades of light orange brown.
Source V. Hartikainen