An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Psychedelic Geometric Background.
Source GDJ
A white version of the very popular linen pattern.
Source Ant Ekşiler
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
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Black paper texture, based on two different images.
Source Atle Mo
Based from Design Kindle
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
White little knobs, coming in at 10x10px. Sweet!
Source Amos
Remixed from a drawing in 'Line and form", Walter Crane, 1914.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Prismatic Groovy Concentric Background No Black
Source GDJ
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
It’s a subtle zebra, in 3D. Oh yes!
Source Mike Warner
Prismatic 3D Isometric Tessellation Pattern 6
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso