ZeroCC tileable mossy (lichen) stone texture, edited from pixabay. CC0
Source Sojan Janso
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Here's a brown background pattern with subtle stripes. I hope you'll like the color. If not, feel free to change it using an image editor, if you know how of course. Personally, I'm using GIMP to create these backgrounds.
Source V. Hartikainen
This ladies and gentlemen, is texturetastic! Love it.
Source Adam Pickering
Very simple, very blu(e). Subtle and nice.
Source Seb Jachec
Looks like an old wall. I guess that’s it then?
Source Viahorizon
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
From a drawing in 'Cassell's Library of English Literature', Henry Morley, 1883.
Source Firkin
Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
A seamlessly tile-able grunge background image.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A free seamless background with pink spots.
Source V. Hartikainen
All good things come in threes, so I give you the third in my little concrete wall series.
Source Atle Mo
Number five from the same submitter, makes my job easy.
Source Dima Shiper
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Dark Tile-able Grunge Texture. I think this texture can be classified as grunge. It's free and seamless, as always.
Source V. Hartikainen
Prismatic Groovy Concentric Background No Black
Source GDJ