Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
More Japanese-inspired patterns, Gold Scales this time.
Source Josh Green
Prismatic Hexagonalist Pattern No Background
Source GDJ
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
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
Tile-able Dark Brown Wood Background. Feel free to use it as a background image in your designs or somewhere on the web. By the way, the color seems to be close to Coffee Brown.
Source V. Hartikainen
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A tile-able background for websites with paper-like texture and a grid pattern layered on top of it.
Source V. Hartikainen
The following repeating website background is colored in a blue gray color and resembles a concrete wall or something similar to it.
Source V. Hartikainen
Prismatic Abstract Background Design
Source GDJ
This was formed by distorting an image of a background on Pixabay.
Source Firkin
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
Spice up your next school project with this icon background.
Source Swetha
From a drawing in 'Prose and Verse ', William Linton, 1836.
Source Firkin
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
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
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen