A green background pattern with warped vertical stripes and a grunge look.
Source V. Hartikainen
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
Colored maple leaves scattered on a surface. This is tileable, so it can be used as a background or wallpaper.
Source Eady
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A seamless web background with texture of aged grid paper.
Source V. Hartikainen
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Uses spirals from Pixabay. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Pattern that came out of playing with the 'slinky' plug-in for Paint.net
Source Firkin
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
To get the repeating unit, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
Prismatic Polyskelion Pattern No Background
Source GDJ
Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!
Source Dertig Media
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prepared mostly as a raster in Paint.net and vectorised.
Source Firkin
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars