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
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
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
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
A nice and simple gray stucco material. Great on its own, or as a base for a new pattern.
Source Bartosz Kaszubowski
Same as the black version, but now in shades of gray. Very subtle and fine grained.
Source Atle Mo
Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!
Source Dertig Media
Looks like an old wall. I guess that’s it then?
Source Viahorizon
From a tile that 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
A colourful background drawn originally in paint.net and vectorised in Vector Magic.
Source Firkin
Similar to original, but without gaps in between the arrows. This seamless pattern was created from a rectangular tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern made from the gold Penrose triangle by GDJ and the two remixes
Source Firkin
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
Used the 6th circle pattern designed by Viscious-Speed to create a print that can be used for card making or scrapbooking. Save as a PDF file for the best printing option.
Source Lovinglf