A version without colours blended together to give a different look.
Source Firkin
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
A free seamless background texture that looks like a brown stone wall.
Source V. Hartikainen
A bit strange this one, but nice at the same time.
Source Diogo Silva
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
Here's a dark background pattern that contains a steel grid pattern as a texture. Use it as a website background or for other purposes. It's free!
Source V. Hartikainen
This is a seamless pattern of a woody texture.The original image is here:https://pixabay.com/ja/users/ClassicallyPrinted-1302233/
Source Yamachem
Everyone needs some stardust. Sprinkle it on your next project.
Source Atle Mo
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
This tiled background comes in red and consists of tiles that look like gemstones. It is more for blogs or social profiles, I think.
Source V. Hartikainen
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Colourful background achieved with gradient fills.
Source Firkin
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
Prismatic Polka Dots Mark II 3 No Background
Source GDJ