Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
High detail stone wall with minor cracks and specks.
Source Projecteightyfive
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Derived from a design in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
This one has rusty dark brown texture.
Source V. Hartikainen
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Abstract Geometric Background 4
Source GDJ
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen