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
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The starting point for this was drawn on the web site steamcoded.org/PolyskelionMaker.svg
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
A seamless web background with texture of aged grid paper.
Source V. Hartikainen
The tile can be had by using shift+alt+i on the selected rectangle in Inkscape
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Alternative colour scheme to the original.
Source Firkin
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Super detailed 16×16 tile that forms a beautiful pattern of straws.
Source Pavel
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A repeating gloomy background image. This one consists of a pattern of black chains layered on top of a dark textured background.
Source V. Hartikainen
Vertical lines with a bumpy, yet crisp, feel to it.
Source Raasa
Prismatic Abstract Geometric Background 4
Source GDJ
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Lovely pattern with splattered vintage speckles.
Source David Pomfret
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