I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Remixed from a drawing that was uploaded to Pixabay by DavidZydd
Source Firkin
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Inspired by a drawing seen in 'City of Liverpool', James Picton, 1883.
Source Firkin
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
From a drawing in 'Danmarks Riges Historie af J. Steenstrup, Kr. Erslev, A. Heise, V. Mollerup, J. A. Fridericia, E. Holm, A. D. Jørgensen', 1897.
Source Firkin
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
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
A seamless pale yellow paper background with a pattern of animal tracks.
Source V. Hartikainen
From drawing in 'Musings in Maoriland', Thomas Bracken, 1890.
Source Firkin
Lovely light gray floral motif with some subtle shades.
Source GraphicsWall
This beige background pattern resembles a concrete wall with engravings or something similar to it.
Source V. Hartikainen
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
A background tile for web with abstract repeating texture of dark "stone wall".
Source V. Hartikainen
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber