The following repeating website background is colored in a blue gray color and resembles a concrete wall or something similar to it.
Source V. Hartikainen
Subtle scratches on a light gray background.
Source Andrey Ovcharov
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
The image depicts meshed silhouettes of various things.The original image is an OCAL clipart called "Enter FOSSASIA 2016 #IoT T-shirt Design Contest" uploaded by "openclipart".Thanks.
Source Yamachem
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Prismatic Curved Diamond Pattern 7 No Background
Source GDJ
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
The original enhanced with some gradients.
Source Firkin
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
Remixed from a JPG that was uploaded to Pixabay by theasad121
Source Firkin
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin