A comeback for you: the popular Escheresque, now in black.
Source Patten
Continuing the geometric trend, here is one more.
Source Mike Warner
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
A seamless pattern with green and yellow diagonal lines on top of a white dotted background.
Source V. Hartikainen
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
More Japanese-inspired patterns, Gold Scales this time.
Source Josh Green
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
Prismatic Abstract Background Design
Source GDJ
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
Prismatic Abstract Background Design No Black
Source GDJ
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Prismatic Polka Dots 3 No Background
Source GDJ
Inspired by a pattern I saw in a 19th century book. This seamless pattern was created from a square tile. To get the tile, select the pattern in Inkscape and use shift+alt+i.
Source Firkin
The image depicts a seamless pattern of a tortoise in tortoiseshell (hexagon).
Source Yamachem
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
Black brick wall pattern. Brick your site up!
Source Alex Parker
The texture of this background image has some similarities with leather, and it's colored in a dark brown color. So, if you are looking for a dark brown background image for your website, this may be an option for you.
Source V. Hartikainen
Prismatic Polka Dots Mark II No Background
Source GDJ
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin