It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
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
Colorful Floral Background No Black
Source GDJ
This is the remix of an Openclipart clipart called "Maze" uploaded by "any_ono_mous".Thanks.This is a seamless pattern of a maze.
Source Yamachem
Could be paper, could be a Polaroid frame – up to you!
Source Chaos
A seamless marble-like texture colored in light blue.
Source V. Hartikainen
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Number five from the same submitter, makes my job easy.
Source Dima Shiper
Prismatic Abstract Background Design No Black
Source GDJ
Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
A comeback for you: the popular Escheresque, now in black.
Source Patten
Square design drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
Just a nice looking textured pattern with faded blue stripes. Well, that's it for today... one background a day, as usual.
Source V. Hartikainen
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
This one needs to be used in small areas; you can see it repeat.
Source Luca
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
Different from the original in being a simple tile stored as a pattern definition, rather than numerous repeated objects. Hence easy and quick to give this pattern to objects of different shapes. To get the tile in Inkscape, select the rectangle and use shift+alt+i.
Source Firkin
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
There are many carbon patterns, but this one is tiny.
Source Designova
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin