This background pattern has futuristic look. So, maybe it could be used on websites or blogs dedicated to video games?!
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Kaleidoscope Prismatic Abstract No Background
Source GDJ
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
Prismatic Abstract Background Design No Black
Source GDJ
The original enhanced with one of Inkscapes's filters.
Source Firkin
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
Inspired by a drawing in 'Poems', James Smith, 1881.
Source Firkin
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Have you wondered about how it feels to be buried alive? Here is the pattern for it.
Source Hendrik Lammers
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker