Batthern #324
 Grid  CC BY-SA 3.0

Sometimes simple really is what you need, and this could fit you well.

Source Factorio.us Collective

 More Textures
Background pattern 309 (colour 2) #1865
 Blue  CC 0

Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.

Source Firkin

Elegant Grid #316
 Wall  CC BY-SA 3.0

This is a hot one. Small, sharp and unique.

Source GraphicsWall

Background pattern 226 (colour 2) #2320
 Green  CC 0

A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.

Source Firkin

Dark Denim #29
 Dark  CC BY-SA 3.0

A dark denim looking pattern. 145×145 pixels.

Source Atle Mo

Inflicted #117
 Grid  CC BY-SA 3.0

Dark squares with some virus-looking dots in the grid.

Source Hugo Loning

Groovepaper #577
 Paper  CC BY-SA 3.0

With a name like this, it has to be hot. Diagonal lines in light shades.

Source Isaac

Connected #348
 Light  CC BY-SA 3.0

White circles connecting on a light gray background.

Source Mark Collins

Retina Dust #915
 Light  CC BY-SA 3.0

First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.

Source Atle Mo

Black Paper #55
 Dark  CC BY-SA 3.0

Black paper texture, based on two different images.

Source Atle Mo
Based from Design Kindle

Background pattern 302 (colour 2) #1893
 Dark  CC 0

The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.

Source Firkin