This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
A free seamless background texture of "timber wall" (colored in dark brown).
Source V. Hartikainen
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
The image depicts a Japanese Edo pattern called "kanoko or 鹿の子" meaning "fawn" which has a fur with small white spots.
Source Yamachem
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Prismatic 3D Isometric Tessellation Pattern 6
Source GDJ
The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background No Black
Source GDJ
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
You were craving more leather, so I whipped this up by scanning a leather jacket.
Source Atle Mo
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
Prismatic Polka Dots 3 No Background
Source GDJ
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
To get the repeating unit, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida