A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
Colour version of the original seamless pattern.
Source Firkin
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Adapted from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
These dots are already worn for you, so you don’t have to.
Source Matt McDaniel
This could be a hippy vintage wallpaper.
Source Tileable Patterns
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Prismatic Hypnotic Pattern No Background
Source GDJ
Sharp but soft triangles in light shades of gray.
Source Pixeden
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
Looks like an old wall. I guess that’s it then?
Source Viahorizon
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
A new take on the black linen pattern. Softer this time.
Source Atle Mo
The following repeating website background is colored in a blue gray color and resembles a concrete wall or something similar to it.
Source V. Hartikainen
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Zero CC tileable ground (#2) cracked, crackled texture, made by me. CC0
Source Sojan Janso
Almost like little fish shells, or dragon skin.
Source Graphiste
Classic 45-degree pattern, light version.
Source Luke McDonald