A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Pattern that came out of playing with the 'slinky' plug-in for Paint.net
Source Firkin
ZeroCC tileable wood boards texture, photographed and made by me. CC0
Source Sojan Janso
A criss-cross pattern similar to one I saw mown into a sports field.
Source Firkin
Sort of reminds me of those old house wallpapers.
Source Tish
Prismatic Curved Diamond Pattern 4 No Background
Source GDJ
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
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
Prismatic Abstract Geometric Background 3
Source GDJ
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin