A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
High detail stone wall with minor cracks and specks.
Source Projecteightyfive
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
This one is quite simple in design, it consists of vertical stripes layered on top of a seamless texture.
Source V. Hartikainen
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Light and tiny, just the way you like it.
Source Rohit Arun Rao
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
Prismatic Curved Diamond Pattern 2 No Background
Source GDJ
A very dark asfalt pattern based off of a photo taken with my iPhone.
Source Atle Mo
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
Prismatic Snowflakes Pattern 2 No Background
Source GDJ
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
Prismatic Rounded Squares Grid 3 No Background
Source GDJ
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
Looks like an old wall. I guess that’s it then?
Source Viahorizon
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
Remixed from a drawing that was uploaded to Pixabay by captenpub.
Source Firkin
To get the repeating unit, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
A repeating background of beige (or is it more vanilla yellow) textured stripes. One more background with stripes.
Source V. Hartikainen