A seamless green background texture. The image is distributed under a Creative Commons License (like all of the images here).
Source V. Hartikainen
The image is a seamless pattern of a fishnet.
Source Yamachem
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
From a drawing in 'La Principauté de Liège et les Pays-Bas au XVIe siècle', Société des Bibliophiles Liégeois ,1887.
Source Firkin
A repeating background with a look of paper. I have added some changes to PatCreator. Now you can share your designs by submitting them to a new gallery section. Start by clicking Edit with PatCreator above.
Source V. Hartikainen
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
Remixed from a raster on Pixabay, that was uploaded by ArtsyBee.
Source Firkin
The tile this is based on can be retrieved 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
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen