Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
A new one called white wall, not by me this time.
Source Yuji Honzawa
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
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
From a drawing in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Square design drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
This is the remix of "Strawberry Pattern Background" uploaded by "GDJ". Thanks. I realigned strawberries so as to get seamless and changed the BG color.
Source Yamachem
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
Derived from a JPG that was uploaded to Pixabay by ractapopulous
Source Firkin
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I. Version with black background.
Source Firkin