The basic shapes never get old. Simple triangle pattern.
Source Atle Mo
Colored maple leaves scattered on a surface. This is tileable, so it can be used as a background or wallpaper.
Source Eady
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
Inspired by a pattern I saw in a 19th century book. This seamless pattern was created from a square tile. To get the tile, select the pattern in Inkscape and use shift+alt+i.
Source Firkin
A fun-looking elastoplast/band-aid pattern. A hint of orange tone in this one.
Source Josh Green
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle 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
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
The image depicts a seamless pattern made using a bird's face.
Source Yamachem
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.