From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
Prismatic Abstract Geometric Background 2
Source GDJ
Prismatic Curved Diamond Pattern 7 No Background
Source GDJ
A seamless textured paper for backgrounds. Colored in pale orange hues.
Source V. Hartikainen
Prismatic Floral Background No Black
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Green Background Pattern
Source V. Hartikainen
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
The image is the remix of "wire-mesh fence seamless pattern" .This is a more minute version of it.Sorry for the file size.Using path>difference in Inkscape, I will cut out any silhouette from this pattern and create a "meshed silhouette".
Source Yamachem
Adapted from an image that was uploaded to Pixabay by Anerma.
Source Firkin
Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo