A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
From a drawing in 'A Guide to the Guildhall of the City of London', John Baddeley, 1898.
Source Firkin
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
Light gray paper pattern with small traces of fiber and some dust.
Source Atle Mo
Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Submitted in a cream color, but you know how I like it.
Source Devin Holmes
A seamless pattern of "sewn stripes" colored in light gray.
Source V. Hartikainen
Prismatic Triangular Background Design Mark II 5
Source GDJ
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
ZeroCC tileabel stone granite texture, edited from pixabay. CC0
Source Sojan Janso
This is the remix of "polka dot seamless pattern".The image depicts polka dot seamless pattern.
Source Yamachem