A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
A bit of scratched up grayness. Always good.
Source Dmitry
A dark gray, sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
From a drawing in 'Kingsdene', Maria Fetherstonehaugh, 1878.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A seamless light gray paper texture with horizontal double lines.
Source V. Hartikainen
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Zero CC Mossy stone tileable texture, photographed and made by me. CC0
Source Sojan Janso
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Prismatic Polka Dots Mark II No Background
Source GDJ
ZeroCC tileabel stone granite texture, edited from pixabay. CC0
Source Sojan Janso
On a large canvas you can see it tiling, but used on smaller areas, it’s beautiful.
Source Paul Phönixweiß
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
Coming in at 666x666px, this is an evil big pattern, but nice and soft at the same time.
Source Atle Mo