A pale olive green background with a seamless texture.
Source V. Hartikainen
Element of beach pattern with background.
Source Rones
Seamless Olive Green Web Background Image
Source V. Hartikainen
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
Remixed from a drawing in 'Очерки Русской Исторіи въ памятникахъ быта', Petr Polevoi, 1879.
Source Firkin
I guess this is inspired by the city of Ravenna in Italy and its stone walls.
Source Sentel
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Just like the black maze, only in light gray. Duh.
Source Peax
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
Prismatic Abstract Geometric Background 4
Source GDJ
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin