CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
The image depicts a seamless pattern of a Japanese family crest called "chidori" in Japanese .A chidori in Japanese means a plover in English.
Source Yamachem
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
Derived from a corner decoration itself found as a jpg on Pixabay.
Source Firkin
Non-seamless pattern drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
A background pattern with green vertical stripes. A new striped background pattern. This time a green one.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
Derived from an image that was uploaded to Pixabay by pugmom40
Source Firkin
A colourful background drawn originally in paint.net and vectorised in Vector Magic.
Source Firkin
Prismatic Groovy Concentric Background No Black
Source GDJ
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
The image depicts a seamless pattern of a fishnet with a plenty of fish.It may be a lucky charm for fishermen.
Source Yamachem
Prismatic Geometric Tessellation Pattern 3 No Background
Source GDJ
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
Classic vertical lines, in all its subtlety.
Source Cody L
Nasty or not, it’s a nice pattern that tiles. Like they all do.
Source Badhon Ebrahim
New paper pattern with a slightly organic feel to it, using some thin threads.
Source Atle Mo
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Used the 6th circle pattern designed by Viscious-Speed to create a print that can be used for card making or scrapbooking. Save as a PDF file for the best printing option.
Source Lovinglf
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić