Embossed lines and squares with subtle highlights.
Source Alex Parker
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
Prismatic Groovy Concentric Background 4
Source GDJ
Prismatic Abstract Background Design No Black
Source GDJ
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Seamless pattern the basic tile for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
Detailed but still subtle and quite original. Lovely gray shades.
Source Kim Ruddock
Colour version of the original pattern.
Source Firkin
This seamless pattern consists of a blue grid on a yellow background.
Source V. Hartikainen
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
The Grid. A digital frontier. I tried to picture clusters of information as they traveled through the computer.
Source Haris Šumić
Derived from a drawing in 'Elfrica. An historical romance of the twelfth century', Charlotte Boger, 1885
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
Super detailed 16×16 tile that forms a beautiful pattern of straws.
Source Pavel
Prismatic Chevrons Pattern 5 With Background
Source GDJ
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Remixed from a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
Prismatic Groovy Concentric Background 2
Source GDJ