From an image on opengameart.org shared by rubberduck.
Source Firkin
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin