Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
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
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
I’m not going to lie – if you submit something with the words Norwegian and Rose in it, it’s likely I’ll publish it.
Source Fredrik Scheide
A seamless design of flowers remixed from a jpg on Pixabay by Prawny.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
Prismatic Floral Background No Black
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso
Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
I scanned a paper coffee cup. You know, in case you need it.
Source Atle Mo
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS
From drawing in 'Musings in Maoriland', Thomas Bracken, 1890.
Source Firkin
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec