Seamless tile drawn in Paint.net and vectorised in Vector Magic.
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
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
The file was named striped lens, but hey – Translucent Fibres works too.
Source Angelica
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This light yellow background pattern consists of an irregular pattern of spots. Here's a light background pattern with yellowish tint.
Source V. Hartikainen
Tweed is back in style – you heard it here first. Also, the @2X version here is great!
Source Simon Leo
Dark pattern with some nice diagonal stitched lines crossing over.
Source Ashton
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
Here's a new paper-like background for free use on personal and commercial projects (this applies to all background patterns here).
Source V. Hartikainen