The image is a seamless pattern of a fishnet.
Source Yamachem
Here's a tile-able wood background image for use in web design.
Source V. Hartikainen
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
Prismatic Hypnotic Pattern No Background
Source GDJ
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
Prismatic Hexagonalist Pattern No Background
Source GDJ
A seamless background pattern of dark brown wood planks.
Source V. Hartikainen
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
Here's a new paper-like background for free use on personal and commercial projects (this applies to all background patterns here).
Source V. Hartikainen