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
Heavily remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
Scanned some rice paper and tiled it up for you. Enjoy.
Source Atle Mo
A seamless background pattern of dark brown wood planks.
Source V. Hartikainen
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
Retro Circles Background 8 No Black
Source GDJ
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Chevrons Pattern 5 With Background
Source GDJ
Nothing like a clean set of bed sheets, huh?
Source Badhon Ebrahim
A black tile-able background with paper-like texture.
Source V. Hartikainen
A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Number 1 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Vertical lines with a bumpy, yet crisp, feel to it.
Source Raasa
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
A new take on the black linen pattern. Softer this time.
Source Atle Mo
Retro Circles Background 4 No Black
Source GDJ
Seamless pattern inspired by a drawing on Pixabay. To get the tile this is formed from, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Feel free to download this "Dark Wood" background texture for your web site. The background tiles seamlessly!
Source V. Hartikainen