Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Seamless SVG vector and JPG backgrounds with faded diagonal stripes. The colors are editable.
Source V. Hartikainen
Sometimes you just need the simplest thing.
Source Fabricio
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
The original has been presented as black on transparent and stored in the pattern definitions. To retrieve the unit tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Prismatic Hexagonalism Pattern No Background
Source GDJ
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
Pattern produced in Paint.net using the Vibrato plug-in.
Source Firkin
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
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
A seamless pattern with green and yellow diagonal lines on top of a white dotted background.
Source V. Hartikainen
From a drawing in 'Handbook of the excursions proposed to be made by the Lincoln Diocesan Architectural Society, on the 27th and 28th of May, 1857', Edward Trollope, 1857.
Source Firkin
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
That’s what it is, a dark dot. Or sort of carbon looking.
Source Tsvetelin Nikolov
An abstract Background pattern of purple twisty patterns.
Source TikiGiki
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen