Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
A free background pattern with abstract green tiles.
Source V. Hartikainen
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Small dots with minor circles spread across to form a nice mosaic.
Source John Burks
Zero CC tileable grass texture, photographed and made by me. CC0
Source Sojan Janso
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
Tile available in Inkscape using shift-alt-i on the selected rectangle
Source Firkin
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
Redrawn based on a drawing in 'По Сѣверо-Западу Россіи' Konstantin Sluchevsky, 1897.
Source Firkin
Colourful background achieved with gradient fills.
Source Firkin