The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
A seamless pattern formed from cross 4. To get the original tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Small dots with minor circles spread across to form a nice mosaic.
Source John Burks
Might not be super subtle, but quite original in its form.
Source Alex Smith
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
The image depicts a Japanese Edo pattern called "kanoko or 鹿の子" meaning "fawn" which has a fur with small white spots.
Source Yamachem
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
Prismatic Geometric Pattern Background 2 No Black
Source GDJ
A seamless pattern of "sewn stripes" colored in light gray.
Source V. Hartikainen
The image depicts a seamless pattern of Japanese Edo pattern called "kikkou-matsu" or "亀甲松" meaning " tortoiseshell-pinetree".The real pinetree is like this: https://jp.pinterest.com/pin/500744052301065077/
Source Yamachem
Inspired by this, I came up with this pattern. Madness!
Source Atle Mo
Geometric triangles seem to be quite hot these days.
Source Pixeden
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
Light gray version of the Binding pattern that looks a bit like fabric.
Source Newbury
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Here's a seamless brown cork board background texture. Feel free to download or reshare if you like.
Source V. Hartikainen
A browner version of the original weathered fence texture.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
An abstract pale yellow paper-like background with stains colored in yellow and green.
Source V. Hartikainen
A seamless paper background texture colored in pale yellow. This seamless texture is ideal for those who need a yellow background image for their website. The texture resembles paper.
Source V. Hartikainen