Black brick wall pattern. Brick your site up!
Source Alex Parker
Abstract Ellipses Background Grayscale
Source GDJ
Fabric-ish patterns are close to my heart. French Stucco to the rescue.
Source Christopher Buecheler
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Alternative colour scheme. 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
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Abstract Background Design
Source GDJ
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
A nice looking light gray background pattern with diagonal stripes.
Source V. Hartikainen
Prismatic Snowflakes Pattern 3 No Background
Source GDJ
Prismatic Polka Dots Mark II 2 No Background
Source GDJ