The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
More in the paper realm, this time with fibers.
Source Jorge Fuentes
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Remixed from a drawing in 'Some account of the Worshipful Company of Ironmongers', John Nicholl, 1866.
Source Firkin
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
A pattern formed from a photograph of a 16th century ceramic tile.
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ