A seamless texture of a rough concrete surface.
Source V. Hartikainen
From a design in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
A light gray background pattern with seamless fabric-like texture and almost unnoticeable stripes.
Source V. Hartikainen
A nice and simple gray stucco material. Great on its own, or as a base for a new pattern.
Source Bartosz Kaszubowski
I love these crisp, tiny, super subtle patterns.
Source Badhon Ebrahim
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
Colourful background achieved with gradient fills.
Source Firkin
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
A free seamless background image with abstract texture of green "curtain".
Source V. Hartikainen
Number 1 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
An attempt for cleaning up the original image in a few steps.
Source Lazur URH
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
A seamless pattern of "sewn stripes" colored in light gray.
Source V. Hartikainen
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Same as the black version, but now in shades of gray. Very subtle and fine grained.
Source Atle Mo
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
A pattern formed from a photograph of a 16th century ceramic tile.
Source Firkin