From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Zero CC bark from fur tree tileable texture, photographed and made by me. CC0
Source Sojan Janso
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Number 5 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Same as the black version, but now in shades of gray. Very subtle and fine grained.
Source Atle Mo
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Nice little grid. Would work great as a base on top of some other patterns.
Source Arno Gregorian
Continuing the geometric trend, here is one more.
Source Mike Warner
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A nice and simple gray stucco material. Great on its own, or as a base for a new pattern.
Source Bartosz Kaszubowski