Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
A seamlessly tile-able grunge background image.
Source V. Hartikainen
Gold Triangular Seamless Pattern No Background
Source GDJ
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
Prismatic Hypnotic Pattern No Background
Source GDJ
More carbon fiber for your collections. This time in white or semi-dark gray.
Source Badhon Ebrahim
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Seamless tile drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
A version without colours blended together to give a different look.
Source Firkin
Remixed from a PNG that was uploaded to Pixabay by VictorianLady
Source Firkin
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
Different from the original in being a simple tile stored as a pattern definition, rather than numerous repeated objects. Hence easy and quick to give this pattern to objects of different shapes. To get the tile in Inkscape, select the rectangle and use shift+alt+i.
Source Firkin
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Geometric lines are always hot, and this pattern is no exception.
Source Listvetra
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
A seamless pattern recreated from an image on Pixabay. It is reminiscent of parquet flooring and is formed from a square tile, which can be recovered in Inkscape by selecting the ungrouped rectangle and using shift-alt-I together.
Source Firkin
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen