I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
Based on an image that was uploaded to Pixabay by devanath
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
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
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Black And White Floral Pattern Background Inverse
Source GDJ
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prepared mostly as a raster in Paint.net and vectorised.
Source Firkin
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
Submitted in a cream color, but you know how I like it.
Source Devin Holmes
A comeback for you: the popular Escheresque, now in black.
Source Patten
Same as Silver Scales, but in black. Turn your site into a dragon with this great scale pattern.
Source Alex Parker
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen