Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Prismatic Polka Dots Mark II 2 No Background
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
You know you can’t get enough of these linen-fabric-y patterns.
Source James Basoo
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
Light gray paper pattern with small traces of fiber and some dust.
Source Atle Mo
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
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
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Greyscale version of a pattern that came out of playing with the 'slinky' plug-in for Paint.net
Source Firkin
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Prismatic Curved Diamond Pattern 4 No Background
Source GDJ
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Remixed from a drawing in 'Incidents on a Journey through Nubia to Darfoor', F. Ensor, 1891.
Source Firkin
Luxury pattern, looking like it came right out of Paris.
Source Daniel Beaton