Small Crackle Bright #352
 Light  CC BY-SA 3.0

Light gray pattern with an almost wall tile-like appearance.

Source Markus Tinner

 More Textures
Micro Carbon #7
 Carbon  CC BY-SA 3.0

Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.

Source Atle Mo

Starting Diamond Shape@2X #138
 Light  CC 0

Simple blue and line to mix.

Source SliverKnight

Wood@2X #50
 Wood  CC BY-SA 3.0

Dark wooden pattern, given the subtle treatment. based on texture from Cloaks. https://cloaks.deviantart.com

Source Atle Mo

Background pattern 213 #2412
 Dark  CC 0

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

Floral Seamless Pattern Background #261
 Fabric  CC 0

PDP

Source GDJ

Prismatic Groovy Concentric Background 2@2X #454
 Noise  CC 0

Prismatic Groovy Concentric Background 2

Source GDJ

Retro Circles Background 7 No Black@2X #434
 Unknow  CC 0

Retro Circles Background 7 No Black

Source GDJ

Floral Abstract Pattern Background #217
 Noise  CC 0

PDP

Source GDJ

Prismatic Octagonal Background@2X #440
 Noise  CC 0

Prismatic Octagonal Background

Source GDJ

Green Fibers@2X #92
 Dark  CC BY-SA 3.0

The green fibers pattern will work very well in grayscale as well.

Source Matteo Di Capua

Paper 1 #15
 Paper  CC BY-SA 3.0

A slightly grainy paper pattern with small horizontal and vertical strokes.

Source Atle Mo

Prismatic Groovy Concentric Background 5 #465
 Dark  CC 0

Prismatic Groovy Concentric Background 5

Source GDJ