As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
The original enhanced with one of Inkscapes's filters.
Source Firkin
Prismatic Hexagonalism Pattern No Background
Source GDJ
Same classic 45-degree pattern, dark version.
Source Luke McDonald
A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
The image depicts an edo-era pattern called "same-komon" or "鮫小紋"which looks like a shark skin.The "same" in Japanese means shark in English.
Source Yamachem
Wasn't satisfied with the original's colouring. Too much component transfer and colormatrixes yet the results are lacking a bit. So this time it is a simple black to transparent fade, making it possible remixing easily once there will be other blending modes supported as well. Probably in inkscape 0.92.
Source Lazur URH
Fake or not, it’s quite luxurious.
Source Factorio.us Collective
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Seamless Olive Green Web Background Image
Source V. Hartikainen
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
Prismatic Chevrons Pattern 5 With Background
Source GDJ
A black tile-able background with paper-like texture.
Source V. Hartikainen
One more sharp little tile for you. Subtle circles this time.
Source Blunia
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
Prismatic Triangular Background Design Mark II 5
Source GDJ
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
A chequerboard pattern with a fruit theme. The fruits are from a posting by inkscapeforum.it.
Source Firkin