A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
A pale yellow background pattern with vertical stripes. The stripes are partially faded. I think this background image turned out pretty well, especially those faded stripes.
Source V. Hartikainen
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
Remixed from an image on Pixabay uploaded by Prawny
Source Firkin
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
Lovely pattern with splattered vintage speckles.
Source David Pomfret
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
CC0 and seamless wellington boot pattern.
Source SliverKnight
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
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
A white version of the very popular linen pattern.
Source Ant Ekşiler
More leather, and this time it’s bigger! You know, in case you need that.
Source Elemis
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Pass parameters to the URL or edit the source code variables to configure the graph paper for the division desired.
Source JayNick
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin