I skipped number 3, because it wasn’t all that great. Sorry.
Source Dima Shiper
A free seamless background pattern for use on websites.
Source V. Hartikainen
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
A seamless pattern formed from a tile made from page ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Geometric triangles seem to be quite hot these days.
Source Pixeden
Prismatic Hexagonalist Pattern No Background
Source GDJ
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
A bit simplified version. Although it could be edited out to be simpler. Anyway, this time the tiling is converted to a pattern fill -which is using clipping for the tile's edges.
Source Lazur URH
This seamless pattern consists of a blue grid on a yellow background.
Source V. Hartikainen
An abstract web texture of a polished blue stone (or does it look more like ice).
Source V. Hartikainen
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
With a name like this, it has to be hot. Diagonal lines in light shades.
Source Isaac
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
I love the movie Pineapple Express, and I’m also liking this Pineapple right here.
Source Audee Mirza
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Detailed but still subtle and quite original. Lovely gray shades.
Source Kim Ruddock
Dark wooden pattern, given the subtle treatment. based on texture from Cloaks. https://cloaks.deviantart.com
Source Atle Mo
Heavily remixed from a drawing in 'Barbara Leybourne; a story of eighty years ago', Sarah Hamer, 1889.
Source Firkin