Not so subtle. These tileable wood patterns are very useful.
Source Elemis
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
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
One more sharp little tile for you. Subtle circles this time.
Source Blunia
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
If you’re sick of the fancy 3D, grunge and noisy patterns, take a look at this flat 2D brick wall.
Source Listvetra
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
A seamless pattern made from the gold Penrose triangle by GDJ and the two remixes
Source Firkin
The image is a seamless pattern of a fishnet.
Source Yamachem
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Prismatic Groovy Concentric Background 4
Source GDJ
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
Used a cherry by doctormo to make this seamless pattern
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker
Derived from a corner decoration itself found as a jpg on Pixabay.
Source Firkin
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
Seamless Dark Grunge Texture. Here's a new grunge texture for use as a background.
Source V. Hartikainen