Grid@2X #975
Gray CC BY-SA 3.0There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
More Textures
Background pattern 6 #225
Noise CC 0Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Blu Stripes@2X #618
Fabric CC BY-SA 3.0Very simple, very blu(e). Subtle and nice.
Source Seb Jachec
Epithalamion tailpiece #2527
Dark CC 0From a drawing in 'Cassell's Library of English Literature', Henry Morley, 1883.
Source Firkin
Polonez Pattern #334
Gray CC BY-SA 3.0A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
Mirrored Squares@2X #124
Dark CC BY-SA 3.0Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
Cubes #133
Light CC BY-SA 3.0This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Circular frame 26 #1711
Dark CC 0Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
GPlay@2X #736
Light CC BY-SA 3.0A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
Seamless Gray Stone Background #1028
Stone CC BY-SA 3.0This background image has seamless texture that resembles a surface of gray stone.
Source V. Hartikainen
Prismatic Groovy Concentric Background 5 No Black@2X #468
Dark CC 0Prismatic Groovy Concentric Background 5 No Black
Source GDJ
Background pattern 272 (colour 3) #2055
Red CC 0A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin