The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker
Might not be super subtle, but quite original in its form.
Source Alex Smith
Sometimes you just need the simplest thing.
Source Fabricio
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A version without colours blended together to give a different look.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Prismatic Snowflakes Pattern 2 No Background
Source GDJ
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
From a drawing of the coat of arms of the Ottoman Empire on Wikimedia.
Source Firkin
Prismatic Rounded Squares Grid 3 No Background
Source GDJ
Can’t believe we don’t have this in the collection already! Slick woven pattern with crisp details.
Source Max Rudberg
Green Web Background, Seamless tile.
Source V. Hartikainen
A comeback for you: the popular Escheresque, now in black.
Source Patten
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin