Background pattern 215 (colour 3) #2369
Pink CC 0A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
More Textures
Decorative divider #1995
Yellow CC 0From a drawing of the coat of arms of the Ottoman Empire on Wikimedia.
Source Firkin
Cloth Alike@2X #1094
Light CC BY-SA 3.0You guessed it – looks a bit like cloth.
Source Peax Webdesign
Dark Circles@2X #307
Dark CC BY-SA 3.0People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Floral background 17 #1851
Green CC 0Vector version of a JPG that was uploaded to Pixabay by theasad121
Source Firkin
Vichy #71
Light CC BY-SA 3.0This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
Climpek #775
Grid CC BY-SA 3.0Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
Debut Dark #1014
Dark CC BY-SA 3.0Same classic 45-degree pattern, dark version.
Source Luke McDonald
Background pattern 15 #201
Dark CC 0A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
"Seamless Bark", Website Background. #879
Wood CC BY-SA 3.0This background pattern contains a seamless texture of bark. It's not very realistic, but I think it looks quite nice.
Source V. Hartikainen
Tex2res3 #723
Fabric CC BY-SA 3.0Number 4 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Gold Triangular Seamless Pattern No Background #272
Light CC 0Gold Triangular Seamless Pattern No Background
Source GDJ
Background pattern 272 (colour 2) #2056
Pink CC 0A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Curved Diamond Pattern 5 No Background@2X #544
Diamond CC 0Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
Decorative divider #1943
Dark CC 0Inspired by a drawing in 'Poems', James Smith, 1881.
Source Firkin
Psychedelic #745
Gray CC BY-SA 3.0Geometric triangles seem to be quite hot these days.
Source Pixeden
"Green Stone", Seamless Web Texture #1050
Stone CC BY-SA 3.0A seamless web texture of "green stone".
Source V. Hartikainen
Floral divider 5 #1749
Dark CC 0From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Abstract Water Texture (Seamless) #890
Water CC BY-SA 3.0An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
Contemporary China 2 #1338
Light CC BY-SA 3.0Old China with a modern twist, take two.
Source Adam Charlts