Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Remixed from a drawing in 'Analecta Eboracensia', Thomas Widdrington, 1897.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
This light background pattern has a texture of "frozen" surface with diagonal stripes. Here's an yet another addition to the collection of free website backgrounds.
Source V. Hartikainen
Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom
Did anyone say The Hoff? This pattern is in no way related to Baywatch.
Source Josh Green
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
Zero CC tileable yellow craft paper; scanned and made by me. CC0
Source Sojan Janso
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Colourful background achieved with gradient fills.
Source Firkin
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Black And White Floral Pattern Background Inverse
Source GDJ
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Stefan is hard at work, this time with a funky pattern of squares.
Source Stefan Aleksić
This tiled background comes in red and consists of tiles that look like gemstones. It is more for blogs or social profiles, I think.
Source V. Hartikainen
White circles connecting on a light gray background.
Source Mark Collins
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin