Classic vertical lines, in all its subtlety.
Source Cody L
CC0 and seamless wellington boot pattern.
Source SliverKnight
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS
Luxury pattern, looking like it came right out of Paris.
Source Daniel Beaton
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
Formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
Prismatic Curved Diamond Pattern No Background
Source GDJ
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
Prismatic Abstract Line Art Pattern Background
Source GDJ
From a drawing in 'Hyde Park from Domesday-Book to date', John Ashton, 1896.
Source Firkin
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
Prismatic Geometric Pattern Background
Source GDJ
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Prismatic Triangular Background Design Mark II 5
Source GDJ
A version without colours blended together to give a different look.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin