I guess this is inspired by the city of Ravenna in Italy and its stone walls.
Source Sentel
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
A seamless pattern formed from a tile made from ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Seamless tile drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Prismatic Abstract Geometric Background 5
Source GDJ
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
CC0 and seamless wellington boot pattern.
Source SliverKnight
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
A seamless texture of black leather. I think it will look best when used in headers, footers or sidebars.
Source V. Hartikainen
Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A seamless background pattern with impressed gray dots.
Source V. Hartikainen
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.
Source Firkin
Looks like an old rug or a computer chip.
Source Patutin Sergey
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
A version without colours blended together to give a different look.
Source Firkin