The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
It looks very nice I think.
Source V. Hartikainen
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
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
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
Prismatic Abstract Geometric Background 3
Source GDJ
A dark brown fabric-like background texture with seamless pattern of winding stripes.
Source V. Hartikainen
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
Same classic 45-degree pattern, dark version.
Source Luke McDonald
A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
A new one called white wall, not by me this time.
Source Yuji Honzawa
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars