This could be a hippy vintage wallpaper.
Source Tileable Patterns
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Prismatic Snowflakes Pattern 2 No Background
Source GDJ
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Seamless Dark Grunge Texture. Here's a new grunge texture for use as a background.
Source V. Hartikainen
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Sort of reminds me of those old house wallpapers.
Source Tish
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
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
Prismatic Geometric Tessellation Pattern 3 No Background
Source GDJ
From an image on opengameart.org shared by rubberduck.
Source Firkin
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
Here's a quite bright pink background pattern for use on websites. It doesn't look like a real fur, but it definitely resembles one.
Source V. Hartikainen
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
A beautiful dark wood pattern, superbly tiled.
Source Omar Alvarado
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
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