Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
Pixel by pixel, sharp and clean. Very light pattern with clear lines.
Source M.Ashok
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
This is a hot one. Small, sharp and unique.
Source GraphicsWall
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless paper background colored in pale yellow.
Source V. Hartikainen
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
Seamless Background For Websites. It has a texture similar to cork-board.
Source V. Hartikainen
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A pattern derived from repeating unit cells each derived from part of a mosaic in paint.net. The starting point for the mosaic was a picture of some prawns!
Source Firkin
Prismatic Geometric Pattern Background
Source GDJ
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
Paper model of a tetrahedron. Modelo de papel de um tetraedro.
Source laobc
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
A white version of the very popular linen pattern.
Source Ant Ekşiler
The Grid. A digital frontier. I tried to picture clusters of information as they traveled through the computer.
Source Haris Šumić