Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Never out of fashion and so much hotter than the 45º everyone knows, here is a sweet 60º line pattern.
Source Atle Mo
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This is a remix of "flower seamless pattern".I rotated the original image by 90 degrees.This is a seamless pattern of flowers.These horizontal wavy lines are one of Edo patterns which is called "tatewaku or tachiwaku or 立湧" that represents uprising steam or vapor.
Source Yamachem
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
A comeback for you: the popular Escheresque, now in black.
Source Patten
Derived from a JPG that was uploaded to Pixabay by ractapopulous
Source Firkin
Luxury pattern, looking like it came right out of Paris.
Source Daniel Beaton
Retro Circles Background 4 No Black
Source GDJ
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
An abstract Background pattern of purple twisty patterns.
Source TikiGiki
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
Prismatic Abstract Geometric Background 4
Source GDJ
It’s an egg, in the form of a pattern. This really is 2012.
Source Paul Phönixweiß
Derived from an image that was uploaded to Pixabay by pugmom40
Source Firkin
Lovely light gray floral motif with some subtle shades.
Source GraphicsWall
The tile for this is based on a repeating unit close to a design on Pixabay. It can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
The starting point for this was drawn on the web site steamcoded.org/PolyskelionMaker.svg
Source Firkin
A browner version of the original weathered fence texture.
Source Firkin