Derived from an image that was uploaded to Pixabay by starchim01
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A seamless background texture of old cardboard.
Source V. Hartikainen
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
A seamless tessellation pattern. To get the tile this is formed from, select the pattern in Inkscape and use shift+alt+i.
Source Firkin
The image depicts a seamless pattern of a snow crystal.I referred to a book called ”sekka-zusetsu” or "雪華図説" which means an illustrated explanation about snow crystals.This book was published in 1832 (天保3年) or Edo period.For more about "雪華図説",see here:dl.ndl.go.jp/info:ndljp/pid/2536975
Source Yamachem
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
Prismatic Geometric Pattern Background
Source GDJ
Element of beach pattern with background.
Source Rones
Paper model of a tetrahedron. Modelo de papel de um tetraedro.
Source laobc
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A criss-cross pattern similar to one I saw mown into a sports field.
Source Firkin
Background formed from the original with an emboss effect.
Source Firkin
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
This one has rusty dark brown texture.
Source V. Hartikainen
A free web background image with a seamless concrete-like texture and an Indian-red color.
Source V. Hartikainen
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
Prismatic Basic Pattern 2 No Background
Source GDJ
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett