Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
Remixed from a JPG that was uploaded to Pixabay by theasad121
Source Firkin
Just like the black maze, only in light gray. Duh.
Source Peax
Utilising some flowers from Almeidah. To get the unit tile, 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
Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
An abstract texture of black metal pipes (seamless).
Source V. Hartikainen
The original enhanced with one of Inkscapes's filters.
Source Firkin
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Formed by distorting a JPG from PublicDomainPictures
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