This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Prismatic Basic Pattern 2 No Background
Source GDJ
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i
Source Firkin
Looks like an old wall. I guess that’s it then?
Source Viahorizon
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.
Source Firkin
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
The image depicts a seamless pattern of a tortoise in tortoiseshell (hexagon).
Source Yamachem
This is the third pattern called Dark Denim, but hey, we all love them!
Source Brandon Jacoby
Formed from decorative divider 184 in paint.net. Vectorised with Vector Magic.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The image is a seamless pattern of a fishnet.
Source Yamachem
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Tweed is back in style – you heard it here first. Also, the @2X version here is great!
Source Simon Leo
Floral patterns might not be the hottest thing right now, but you never know when you need it!
Source Lauren
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Prismatic Floral Background No Black
Source GDJ
A light gray fabric pattern with faded vertical stripes.
Source V. Hartikainen
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A seamlessly tileable pink background texture.
Source V. Hartikainen
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn