Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Zero CC tileable Laminate wood texture, photographed and made by me. CC0
Source Sojan Janso
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A rusty grunge background for websites. Feel free to use it in your site's theme.
Source V. Hartikainen
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
This makes me wanna shoot some pool! Sweet green pool table pattern.
Source Caveman
A seamlessly tile-able grunge background image.
Source V. Hartikainen
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
With a name like this, it has to be hot. Diagonal lines in light shades.
Source Isaac
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
Free tiled background with colorful stripes and white splatter.
Source V. Hartikainen
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Dark Tile-able Grunge Texture. I think this texture can be classified as grunge. It's free and seamless, as always.
Source V. Hartikainen
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Prismatic Groovy Concentric Background 2 No Black
Source GDJ