Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
Never out of fashion and so much hotter than the 45º everyone knows, here is a sweet 60º line pattern.
Source Atle Mo
Free tiled background with colorful stripes and white splatter.
Source V. Hartikainen
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Submitted in a cream color, but you know how I like it.
Source Devin Holmes
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
You know, tiny and sharp. I’m sure you’ll find a use for it.
Source Atle Mo
A seamless marble-like texture colored in light blue.
Source V. Hartikainen
Tiny little fibers making a soft and sweet look.
Source Badhon Ebrahim
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Derived from a corner decoration itself found as a jpg on Pixabay.
Source Firkin
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Small dots with minor circles spread across to form a nice mosaic.
Source John Burks
Remixed from a drawing in 'Canadian forest industries July-December', 1915
Source Firkin
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Number five from the same submitter, makes my job easy.
Source Dima Shiper
Not the Rebel alliance, but a dark textured pattern.
Source Hendrik Lammers