Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
Original seamless pattern with an Inkscape filter.
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
emixed from a JPG that was uploaded to Pixabay by Kyotime
Source Firkin
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Little x’es, noise and all the stuff you like. Dark like a Monday, with a hint of blue.
Source Tom McArdle
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Prismatic Groovy Concentric Background 4
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
Light gray version of the Binding pattern that looks a bit like fabric.
Source Newbury
A free grid paper background pattern for using on web sites.
Source V. Hartikainen
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
Sort of like the back of a wooden board. Light, subtle, and stylish, just the way we like it!
Source Nikolalek
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Prismatic Abstract Geometric Background 5
Source GDJ
From a drawing in 'A Life Interest', Mrs Alexander, 1888.
Source Firkin
The name is totally random, but hey, it sounds good.
Source Atle Mo
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i
Source Firkin
A background pattern with wavy green vertical stripes. This one has green stripes on a white background. Download if you like it.
Source V. Hartikainen