This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
From a drawing in 'A Rolling Stone. A tale of wrongs and revenge', John Hartley, 1878.
Source Firkin
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
From a design in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
The following orange background pattern resembles a honeycomb.
Source V. Hartikainen
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
A seamless texture of an abstract wall colored in shades of light orange brown.
Source V. Hartikainen
White little knobs, coming in at 10x10px. Sweet!
Source Amos
Just like your old suit, all striped and smooth.
Source Alex Berkowitz
A very dark asfalt pattern based off of a photo taken with my iPhone.
Source Atle Mo
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
The tile this is based on can be retrieved 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
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A bit strange this one, but nice at the same time.
Source Diogo Silva
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic