This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Sort of reminds me of those old house wallpapers.
Source Tish
This is the third pattern called Dark Denim, but hey, we all love them!
Source Brandon Jacoby
Sharp pixel pattern, just like the good old days.
Source Paridhi
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
A seamless pattern formed from a square tile based on a jpg on Pixabay. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
He influenced us all. “Don’t be sad because it’s over. Smile because it happened.”
Source Atle Mo
A free green background pattern with a pattern of rhombuses on a seamless texture. Feel free to use it as a tiled background image on your web site.
Source V. Hartikainen
Remixed from a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
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.
Source Firkin
Prismatic Hexagonalist Pattern No Background
Source GDJ
An aged paper background tile with smeared and pressed text.
Source V. Hartikainen
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin