A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
Remixed from a JPG that was uploaded to Pixabay by theasad121
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
Prismatic Geometric Pattern Background 2 No Black
Source GDJ
Same as the black version, but now in shades of gray. Very subtle and fine grained.
Source Atle Mo
A pattern drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
Derived from an image that was uploaded to Pixabay by darkmoon1968
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
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
A seamless pattern based on a tile that can be achieved 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
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Has nothing to do with toast, but it’s nice and subtle.
Source Pippin Lee
Prismatic Abstract Geometric Background 5
Source GDJ