From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This is a seamless pattern of regular hexagon which has a honeycomb structure.
Source Yamachem
Remixed from a JPG that was uploaded to Pixabay by susanlu4esm
Source Firkin
Seamless Prismatic Geometric Pattern With Background
Source GDJ
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
A pattern formed from repeated instances of corner decoration 8. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Remixed from a drawing that was uploaded to Pixabay by captenpub.
Source Firkin
A comeback for you: the popular Escheresque, now in black.
Source Patten
It’s big, it’s gradient—and it’s square.
Source Brankic1979
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
Prismatic Geometric Pattern Background
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
All good things come in threes, so I give you the third in my little concrete wall series.
Source Atle Mo
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
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
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This is sort of fresh, but still feels a bit old school.
Source Martuchox
Prismatic Groovy Concentric Background 2
Source GDJ
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
Produced using the clouds, flames and glass blocks plug-ins in Paint.net and the resulting .PNG vectorised with Vector Magic.
Source Firkin