A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Subtle scratches on a light gray background.
Source Andrey Ovcharov
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
Zero CC tileable hard cover green book, scanned and made by me. CC0
Source Sojan Janso
A comeback for you: the popular Escheresque, now in black.
Source Patten
This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
This light yellow background pattern consists of an irregular pattern of spots. Here's a light background pattern with yellowish tint.
Source V. Hartikainen
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
I love these crisp, tiny, super subtle patterns.
Source Badhon Ebrahim
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Prismatic Geometric Pattern Background No Black
Source GDJ
The image depicts a seamless pattern which includes hexagonally-aligned gourds with BG in light-brown.
Source Yamachem
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A criss-cross pattern similar to one I saw mown into a sports field.
Source Firkin
Sounds like something from World of Warcraft. Has to be good.
Source Tony Kinard
I love the movie Pineapple Express, and I’m also liking this Pineapple right here.
Source Audee Mirza
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman