This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
Prismatic Abstract Line Art Pattern Background
Source GDJ
A dark brown fabric-like background texture with seamless pattern of winding stripes.
Source V. Hartikainen
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A light brushed aluminum pattern for your pleasure.
Source Tim Ward
A free seamless background pattern for use on websites.
Source V. Hartikainen
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
Tweed is back in style – you heard it here first. Also, the @2X version here is great!
Source Simon Leo
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Derived from a drawing in 'Elfrica. An historical romance of the twelfth century', Charlotte Boger, 1885
Source Firkin
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Derived from a JPG that was uploaded to Pixabay by ractapopulous
Source Firkin
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
Seamless Olive Green Web Background Image
Source V. Hartikainen
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
8 by 8 pixels, and just what the title says.
Source pixilated
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This tiled background comes in red and consists of tiles that look like gemstones. It is more for blogs or social profiles, I think.
Source V. Hartikainen