Not so subtle. These tileable wood patterns are very useful.
Source Elemis
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
Traced from a drawing in 'Household Stories from the Collection of the Brothers Grimm', Wilhelm Carl Grimm , 1882.
Source Firkin
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
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
Lovely pattern with some good-looking non-random noise lines.
Source Zucx
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I. A version of the original with random colors.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Green Web Background, Seamless tile.
Source V. Hartikainen
This background image has seamless texture that resembles a surface of gray stone.
Source V. Hartikainen
Tile-able Dark Brown Wood Background. Feel free to use it as a background image in your designs or somewhere on the web. By the way, the color seems to be close to Coffee Brown.
Source V. Hartikainen
Colour version that is close to the original drawing uploaded to Pixabay by pencilparker.
Source Firkin
This one needs to be used in small areas; you can see it repeat.
Source Luca
Black And White Floral Pattern Background from PDP.
Source GDJ
Number 1 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Prismatic Curved Diamond Pattern 7 No Background
Source GDJ
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
Nothing like a clean set of bed sheets, huh?
Source Badhon Ebrahim
So tiny, just 7 by 7 pixels – but still so sexy. Ah yes.
Source Dmitriy Prodchenko
From a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo