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
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Here's an yet another background for websites, with a seamless texture of wood planks this time.
Source V. Hartikainen
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
Feel free to download this "Dark Wood" background texture for your web site. The background tiles seamlessly!
Source V. Hartikainen
This is a hot one. Small, sharp and unique.
Source GraphicsWall