Not so subtle. These tileable wood patterns are very useful.
Source Elemis
I’m starting to think I have a concrete wall fetish.
Source Atle Mo
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A version without colours blended together to give a different look.
Source Firkin
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
Inspired by a drawing in 'Poems', James Smith, 1881.
Source Firkin
This background pattern has futuristic look. So, maybe it could be used on websites or blogs dedicated to video games?!
Source V. Hartikainen
Use shift+alt+i on the selected rectangle in Inkscape to get the tile this is based on
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Original minus the background
Source Firkin
This one is quite simple in design, it consists of vertical stripes layered on top of a seamless texture.
Source V. Hartikainen
Lovely light gray floral motif with some subtle shades.
Source GraphicsWall