Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
We have some linen patterns here, but none that are stressed. Until now.
Source Jordan Pittman
This is a hot one. Small, sharp and unique.
Source GraphicsWall
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
Zero CC tileable brick texture, photographed and made by me. CC0
Source Sojan Janso
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
Prismatic Curved Diamond Pattern No Background
Source GDJ
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Black And White Floral Pattern Background from PDP.
Source GDJ
This is sort of fresh, but still feels a bit old school.
Source Martuchox