A comeback for you: the popular Escheresque, now in black.
Source Patten
Light gray version of the Binding pattern that looks a bit like fabric.
Source Newbury
Lovely pattern with some good-looking non-random noise lines.
Source Zucx
The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay, CC0
Source Sojan Janso
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
I love these crisp, tiny, super subtle patterns.
Source Badhon Ebrahim
A seamless texture of worn out "cardboard".
Source V. Hartikainen
Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Seamless Olive Green Web Background Image
Source V. Hartikainen
Zero CC tileable dry grass texture, photographed and made by me. CC0
Source Sojan Janso
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
Here I have tried to create something that would look like maple wood. Not sure how well it's turned out, but at least it looks like wood.
Source V. Hartikainen
Background pattern made in "Grunge-Like" style. Available in both SVG and JPG formats. Edit to your needs then click the download button.
Source V. Hartikainen
Pass parameters to the URL or edit the source code variables to configure the graph paper for the division desired.
Source JayNick
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
Can’t believe we don’t have this in the collection already! Slick woven pattern with crisp details.
Source Max Rudberg