Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Prismatic Polyskelion Pattern No Background
Source GDJ
A background pattern with green vertical stripes. A new striped background pattern. This time a green one.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
This one is quite simple in design, it consists of vertical stripes layered on top of a seamless texture.
Source V. Hartikainen
Prismatic Groovy Concentric Background 3
Source GDJ
More in the paper realm, this time with fibers.
Source Jorge Fuentes
This is a grid, only it’s noisy. You know. Reminds you of those printed grids you draw on.
Source Vectorpile
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Zero CC tileable hard cover green book, scanned and made by me. CC0
Source Sojan Janso
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady