Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
A version without colours blended together to give a different look.
Source Firkin
A repeating background of beige (or is it more vanilla yellow) textured stripes. One more background with stripes.
Source V. Hartikainen
A pattern drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
I love the movie Pineapple Express, and I’m also liking this Pineapple right here.
Source Audee Mirza
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
This was submitted in a beige color, hence the name. Now it’s a gray paper pattern.
Source Konstantin Ivanov
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
From a drawing in 'Az Osztrák-Magyar Monarchia irásban és képben', 1885.
Source Firkin
The following repeating website background is colored in a blue gray color and resembles a concrete wall or something similar to it.
Source V. Hartikainen
Actually remixed from a pattern on Pixabay. But then noticed a very similar one on Openclipart.org uploaded by btj51q2.
Source Firkin
Has nothing to do with toast, but it’s nice and subtle.
Source Pippin Lee
You know you love wood patterns, so here’s one more.
Source Richard Tabor
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Prismatic Hexagonalism Pattern No Background
Source GDJ
The texture of this background image has some similarities with leather, and it's colored in a dark brown color. So, if you are looking for a dark brown background image for your website, this may be an option for you.
Source V. Hartikainen
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