The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
The following orange background pattern resembles a honeycomb.
Source V. Hartikainen
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Colour version of the original pattern inspired by the front cover of 'Old and New Paris', Henry Edwards, 1894.
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Dark Tile-able Grunge Texture. I think this texture can be classified as grunge. It's free and seamless, as always.
Source V. Hartikainen
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
Fix side and a seamless pattern formed from circles.
Source SliverKnight
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
This is a seamless pattern of regular hexagon which has a honeycomb structure.
Source Yamachem
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Retro Circles Background 8 No Black
Source GDJ
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
Number five from the same submitter, makes my job easy.
Source Dima Shiper
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin