Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
A free seamless background texture that looks like a brown stone wall.
Source V. Hartikainen
Same as Silver Scales, but in black. Turn your site into a dragon with this great scale pattern.
Source Alex Parker
The base gradient edited so now more details are rendered.
Source Lazur URH
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
Continuing the geometric trend, here is one more.
Source Mike Warner
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Prismatic Polka Dots Mark II 2 No Background
Source GDJ
Seamless pattern formed from a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
Inspired by a JPG that was uploaded to Pixabay by kokon_art
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
A dark metallic background with a pattern of stamped dots. Here's a dark "metallic" background pattern for you.
Source V. Hartikainen
Submitted in a cream color, but you know how I like it.
Source Devin Holmes
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
Hey, you never know when you’ll need a bird pattern, right?
Source Pete Fecteau