Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
This background pattern looks like bamboo to me. Feel free to download it for your website (for your blog perhaps?).
Source V. Hartikainen
I have no idea what J Boo means by this name, but hey – it’s hot.
Source j Boo
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Might not be super subtle, but quite original in its form.
Source Alex Smith
Colour version that is close to the original drawing uploaded to Pixabay by pencilparker.
Source Firkin
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
A seamless pattern made from the gold Penrose triangle by GDJ and the two remixes
Source Firkin
Orange-red pattern for tiled backgrounds.
Source V. Hartikainen
No relation to the band, but damn it’s subtle!
Source Thomas Myrman
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Remixed from a drawing in 'A Girl in Ten Thousand', Elizabeth Meade, 1896.
Source Firkin
The base gradient edited so now more details are rendered.
Source Lazur URH
This is the remix of an OCAL clipart called "Art Nouveau ornament" uploaded by "microcosme".Thanks.This is a seamless pattern of an Art Nouveau ornament.
Source Yamachem
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin