A comeback for you: the popular Escheresque, now in black.
Source Patten
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
Pattern formed from simple shapes. Black version.
Source Firkin
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
A dark gray, sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
A pale olive green background with a seamless texture.
Source V. Hartikainen
Abstract Ellipses Background Grayscale
Source GDJ
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Pixel by pixel, sharp and clean. Very light pattern with clear lines.
Source M.Ashok
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
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
An abstract web texture of a polished blue stone (or does it look more like ice).
Source V. Hartikainen
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
It looks very nice I think.
Source V. Hartikainen
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
This is the remix of "Tileable Wave Pattern 2" uploaded by "Arvin61r58".Thanks.I added a wire-mesh fence seamless pattern as a lower layer.
Source Yamachem
Remixed from a drawing in 'Prehistoric Man: researches into the origin of civilisation in the old and the new world', Daniel Wilson, 1876.
Source Firkin
As the original image 's page size is too large for its image size, I remixed it.
Source Yamachem
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin