Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
Kaleidoscope Prismatic Abstract No Background
Source GDJ
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
A version without colours blended together to give a different look.
Source Firkin
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
The original enhanced with some gradients.
Source Firkin
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A dark striped seamless pattern suitable for use as a background on websites.
Source V. Hartikainen
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
White handmade paper pattern with small bumps.
Source Marquis
Geometric lines are always hot, and this pattern is no exception.
Source Listvetra
Farmer could be some sort of fabric pattern, with a hint of green.
Source Fabian Schultz
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
The following free background pattern has glossy diagonal stripes as a texture to it, and it's colored in a light blue gray color. This background pattern is suitable for using in web design or any other graphic design projects. This applies to all background patterns here.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
This is a hot one. Small, sharp and unique.
Source GraphicsWall
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
A free seamless background pattern for use on websites.
Source V. Hartikainen