A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
Prismatic Geometric Tessellation Pattern 3 No Background
Source GDJ
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
Zero CC tillable hard cover red book with X shape marks. Scanned and made by me.
Source Sojan Janso
Zero CC tileable yellow craft paper; scanned and made by me. CC0
Source Sojan Janso
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Remixed from a drawing in 'Analecta Eboracensia', Thomas Widdrington, 1897.
Source Firkin
On a large canvas you can see it tiling, but used on smaller areas, it’s beautiful.
Source Paul Phönixweiß
This was formed by distorting an image of a background on Pixabay.
Source Firkin
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
More carbon fiber for your collections. This time in white or semi-dark gray.
Source Badhon Ebrahim
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
These dots are already worn for you, so you don’t have to.
Source Matt McDaniel
Submitted as a black pattern, I made it light and a few steps more subtle.
Source Andy
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
A seamless pattern formed from miutopia's cakes on a tablecloth.
Source Firkin