This was formed by distorting an image of a background on Pixabay.
Source Firkin
Number five from the same submitter, makes my job easy.
Source Dima Shiper
A comeback for you: the popular Escheresque, now in black.
Source Patten
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Fake or not, it’s quite luxurious.
Source Factorio.us Collective
If you don’t like cream and pixels, you’re in the wrong place.
Source Mizanur Rahman
This is a remix of "flower seamless pattern".I rotated the original image by 90 degrees.This is a seamless pattern of flowers.These horizontal wavy lines are one of Edo patterns which is called "tatewaku or tachiwaku or 立湧" that represents uprising steam or vapor.
Source Yamachem
A seamless pattern formed from a tile made from ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Just like your old suit, all striped and smooth.
Source Alex Berkowitz
A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
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
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Remixed from a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
A repeating background with dark brown stone-like texture and abstract pattern that looks like tree trunks.
Source V. Hartikainen
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
Seamless Green Tile Background
Source V. Hartikainen
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin