A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A bit of scratched up grayness. Always good.
Source Dmitry
Alternative colour scheme for the original floral pattern.
Source Firkin
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
Colored maple leaves scattered on a surface. This is tileable, so it can be used as a background or wallpaper.
Source Eady
A seamless pattern formed from background pattern 102
Source Firkin
This is the third pattern called Dark Denim, but hey, we all love them!
Source Brandon Jacoby
Prismatic Abstract Background Design No Black
Source GDJ
If you don’t like cream and pixels, you’re in the wrong place.
Source Mizanur Rahman
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
Alternative colour scheme for the original floral pattern.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Psychedelic Geometric Background No Black
Source GDJ
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
A yellow tiled background... Blurriness, bokeh effect and rectangles pattern in one mix.
Source V. Hartikainen