From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Seamless Prismatic Quadrilateral Line Art Pattern No Background
Source GDJ
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Derived from a design in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Prismatic Basic Pattern 2 No Background
Source GDJ
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
The following orange background pattern resembles a honeycomb.
Source V. Hartikainen
Zero CC tileable moss or lichen covered stone texture, edited from pixabay. CC0
Source Sojan Janso
Have you wondered about how it feels to be buried alive? Here is the pattern for it.
Source Hendrik Lammers
A floral background formed from numerous clones of flower 117.
Source Firkin