A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
A seamless pattern formed from a tile made from ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Hypnotic Pattern No Background
Source GDJ
Remixed from an image that was uploaded to Pixabay by KirstenStar
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
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Continuing the geometric trend, here is one more.
Source Mike Warner
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
Number 5 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Prismatic Polka Dots Mark II 3 No Background
Source GDJ
Hey, you never know when you’ll need a bird pattern, right?
Source Pete Fecteau
Prismatic Abstract Background Design No Black
Source GDJ
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing of the coat of arms of the Ottoman Empire on Wikimedia.
Source Firkin
Floral patterns will never go out of style, so enjoy this one.
Source Lasma
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso