People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
An abstract texture of black metal pipes (seamless).
Source V. Hartikainen
Prismatic Hypnotic Pattern No Background
Source GDJ
This is the remix of an OCAL clipart called "Art Nouveau ornament" uploaded by "microcosme".Thanks.This is a seamless pattern of an Art Nouveau ornament.
Source Yamachem
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
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
Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
A white version of the very popular linen pattern.
Source Ant Ekşiler
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
The image depicts the Japanese Edo pattern called "seigaiha" or "青海波" meaning "blue -sea- wave".I hope it's suitable for the summer season.
Source Yamachem
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
Lovely light gray floral motif with some subtle shades.
Source GraphicsWall
Black brick wall pattern. Brick your site up!
Source Alex Parker
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
Subtle scratches on a light gray background.
Source Andrey Ovcharov
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin