Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
A lot of people like the icon patterns, so here’s one for your restaurant blog.
Source Andrijana Jarnjak
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
Prismatic Hexagonalist Pattern No Background
Source GDJ
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
This background pattern contains a seamless texture of bark. It's not very realistic, but I think it looks quite nice.
Source V. Hartikainen
A pattern formed from a photograph of a 16th century ceramic tile.
Source Firkin
The image depicts meshed silhouettes of various things.The original image is an OCAL clipart called "Enter FOSSASIA 2016 #IoT T-shirt Design Contest" uploaded by "openclipart".Thanks.
Source Yamachem
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Derived from a design in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
Did anyone say The Hoff? This pattern is in no way related to Baywatch.
Source Josh Green
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Prismatic Snowflakes Pattern No Background
Source GDJ
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Classic vertical lines, in all its subtlety.
Source Cody L
Utilising a bird from s-light and some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
High detail stone wall with minor cracks and specks.
Source Projecteightyfive
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Original minus the background
Source Firkin
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Seamless Light Background Texture.
Source V. Hartikainen
Inspired by a pattern found in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin