A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
A dark gray, sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
Prismatic Triangular Background Design Mark II 5
Source GDJ
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Sort of reminds me of those old house wallpapers.
Source Tish
Prismatic Groovy Concentric Background 2
Source GDJ
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
One more sharp little tile for you. Subtle circles this time.
Source Blunia
Colour version of the original pattern inspired by the front cover of 'Old and New Paris', Henry Edwards, 1894.
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
A seamless textured paper for backgrounds. Colored in pale orange hues.
Source V. Hartikainen
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin