Not so subtle. These tileable wood patterns are very useful.
Source Elemis
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
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
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
Prismatic Curved Diamond Pattern 7 No Background
Source GDJ
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Washi (和紙?) is a type of paper made in Japan. Here’s the pattern for you!
Source Carolynne
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
Original minus the background
Source Firkin
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
Very simple, very blu(e). Subtle and nice.
Source Seb Jachec
This is the remix of "Tileable Wave Pattern 2" uploaded by "Arvin61r58".Thanks.I added a wire-mesh fence seamless pattern as a lower layer.
Source Yamachem
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Geometric triangles seem to be quite hot these days.
Source Pixeden