Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A light gray fabric pattern with faded vertical stripes.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Heavily remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
I’m starting to think I have a concrete wall fetish.
Source Atle Mo
A seamless pale yellow paper background with a pattern of animal tracks.
Source V. Hartikainen
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Remixed from a JPG that was uploaded to Pixabay by theasad121
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
Abstract Ellipses Background Grayscale
Source GDJ
A seamless background colored in pale orange. It has a paper like texture with diagonal grid pattern.
Source V. Hartikainen
A floral background formed from numerous clones of flower 117.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This could be a hippy vintage wallpaper.
Source Tileable Patterns
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin