It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
Wild Oliva or Oliva Wilde? Darker than the others, sort of a medium dark pattern.
Source Badhon Ebrahim
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
A beautiful dark wood pattern, superbly tiled.
Source Omar Alvarado
Here is a new seamless wood texture for using as blog or website backgrounds.
Source V. Hartikainen
Background formed from the original with an emboss effect
Source GDJ
Sharp but soft triangles in light shades of gray.
Source Pixeden
This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Green Web Background, Seamless tile.
Source V. Hartikainen
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
A seamless pattern the starting point for which was a 'light rays' rendering in Paint.net.
Source Firkin