A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
Continuing the geometric trend, here is one more.
Source Mike Warner
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
Awesome name, great pattern. Who does not love space?
Source Nick Batchelor
The image depicts a seamless pattern made using a bird's face.
Source Yamachem
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Dark blue concrete wall with some small dust spots.
Source Atle Mo
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
A seamless pattern formed from background pattern 102
Source Firkin
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
Prismatic Groovy Concentric Background 4
Source GDJ
Utilising a bird from s-light and some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
The image is a seamless pattern of a fishnet.
Source Yamachem
A seamless pattern based on a tile that can be achieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin