This is so subtle you need to bring your magnifier!
Source Carlos Valdez
A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
A background pattern with blue on white vertical stripes.
Source V. Hartikainen
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
The following repeating website background is colored in a blue gray color and resembles a concrete wall or something similar to it.
Source V. Hartikainen
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
This could be a hippy vintage wallpaper.
Source Tileable Patterns
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
Prismatic Triangular Background Design Mark II 5
Source GDJ
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
This seamless web background texture looks like gray stone. It's great for using as a background image on web pages, or on some of their elements. Anyway, I hope you will find use for it.
Source V. Hartikainen