A comeback for you: the popular Escheresque, now in black.
Source Patten
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
Colorful Floral Background 3 No Black
Source GDJ
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
It’s like Shine Dotted’s sister, only rotated 45 degrees.
Source mediumidee
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
A seamless textured paper for backgrounds. Colored in pale orange hues.
Source V. Hartikainen
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
Zero CC asphalt, pavement, texture, photographed and made by me. CC0 WARNING I FOUND A SEAM ON THIS TEXTURE
Source Sojan Janso
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
More Japanese-inspired patterns, Gold Scales this time.
Source Josh Green
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo