Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
A free seamless background pattern for use on websites.
Source V. Hartikainen
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
Nothing like a clean set of bed sheets, huh?
Source Badhon Ebrahim
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A seamless web background with texture of aged grid paper.
Source V. Hartikainen
Sometimes you just need the simplest thing.
Source Fabricio
Prismatic Hexagonalism Pattern No Background
Source GDJ
Prismatic Geometric Pattern Background 2
Source GDJ
Seamless Green Tile Background
Source V. Hartikainen
From a drawing in 'Worsborough; its historical associations and rural attractions', Joseph Wilkinson, 1879.
Source Firkin
The basic shapes never get old. Simple triangle pattern.
Source Atle Mo
A seamless pattern formed from a modified version of rwwgub's tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Nasty or not, it’s a nice pattern that tiles. Like they all do.
Source Badhon Ebrahim
Dark blue concrete wall with some small dust spots.
Source Atle Mo
8 by 8 pixels, and just what the title says.
Source pixilated
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
The image a seamless pattern of a wire-mesh fence.I want you to use this pattern as a lower layer.
Source Yamachem
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin