Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Almost like little fish shells, or dragon skin.
Source Graphiste
The basic shapes never get old. Simple triangle pattern.
Source Atle Mo
Zero CC tileable hard cover cells, skin like, book texture. 4K, Scanned and made by me CC0
Source Sojan Janso
The image a seamless pattern derived from a weed which I can't identify.The original weed image is from here:https://jp.pinterest.com/pin/500744052301423641/
Source Yamachem
Sort of reminds me of those old house wallpapers.
Source Tish
Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
This is sort of fresh, but still feels a bit old school.
Source Martuchox
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
This light blue background pattern is quite pleasing to the eye, it consists of a tiny rough grid pattern, which is seamless by design. That's it, if you like the color, you can use this seamless pattern in a web design without making any further modifications to it.
Source V. Hartikainen
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
This yellow background consists of a pattern of glossy gold buttons arranged in polka dot style on a seamless texture. Here's a pale yellow background pattern. Feel free to use it for your needs!
Source V. Hartikainen
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
Same as the black version, but now in shades of gray. Very subtle and fine grained.
Source Atle Mo