Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A seamless pattern formed from a square tile based on a jpg on Pixabay. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
Dark wooden pattern, given the subtle treatment. based on texture from Cloaks.
A seamless pattern formed from background pattern 102
Source Firkin
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
You know you love wood patterns, so here’s one more.
Source Richard Tabor
A light gray background pattern with seamless fabric-like texture and almost unnoticeable stripes.
Source V. Hartikainen
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Colour version of the original pattern.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Here's a tile-able wood background image for use in web design.
Source V. Hartikainen
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 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
Remixed from an image on Pixabay uploaded by Prawny
Source Firkin
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A gray background pattern with a texture of textile. Suits perfectly for web design.
Source V. Hartikainen
Fabric-ish patterns are close to my heart. French Stucco to the rescue.
Source Christopher Buecheler
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Might not be super subtle, but quite original in its form.
Source Alex Smith