Inspired by a design found in 'Konstantinápolyi emlékeim', Miklos Chriszto, 1893.
Source Firkin
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
A seamlessly tileable pink background texture.
Source V. Hartikainen
A free seamless background pattern for use on websites.
Source V. Hartikainen
The classic notebook paper with horizontal stripes.
Source Are Sundnes
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
A textured orange background pattern with vertical stripes.
Source V. Hartikainen
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
The image depicts a seamless pattern of Japanese Edo pattern called "kikkou-matsu" or "亀甲松" meaning " tortoiseshell-pinetree".The real pinetree is like this: https://jp.pinterest.com/pin/500744052301065077/
Source Yamachem