White carbon@2X #12
 Carbon  CC BY-SA 3.0

Same as the black version, but now in shades of gray. Very subtle and fine grained.

Source Atle Mo

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White Plaster@2X #369
 Wall  CC BY-SA 3.0

Sweet and subtle white plaster with hints of noise and grunge.

Source Phil Maurer

Background pattern 259 (colour 3) #2130
 Colorful  CC 0

Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

Seamless Core Pattern 6 #170
 Dark  CC 0

Seamless Core Pattern 6

Source GDJ

Abstract Tiled Background Extended 10 #521
 Noise  CC 0

Abstract Tiled Background Extended 10

Source GDJ

Prismatic Groovy Concentric Background 3 No Black@2X #460
 Noise  CC 0

Prismatic Groovy Concentric Background 3 No Black

Source GDJ

Background pattern 10 #216
 Noise  CC 0

A pattern drawn in Paint.net and vectorized in Vector Magic.

Source Firkin

Retro Circles Background 6 #428
 Noise  CC 0

Retro Circles Background 6

Source GDJ

Prismatic Groovy Concentric Background 4 No Black@2X #464
 Noise  CC 0

Prismatic Groovy Concentric Background 4 No Black

Source GDJ

Prismatic Dots Background 4@2X #508
 Noise  CC 0

Prismatic Dots Background 4

Source GDJ

Floral design 71 #2429
 Dark  CC 0

From a drawing in 'From Snowdon to the Sea. Striking stories of North and South Wales', Marie Trevelyan, 1895.

Source Firkin

Background pattern 308 (colour 3) #1870
 Colorful  CC 0

Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.

Source Firkin

Seamless Wood Pattern #889
 Wood  CC BY-SA 3.0

A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.

Source V. Hartikainen

Graphene pattern 2 #2234
 Dark  CC 0

Formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

Handmade Paper@2X #38
 Paper  CC BY-SA 3.0

White handmade paper pattern with small bumps.

Source Marquis

Desert Camo Print #255
 Fabric  CC 0

Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.

Source Eady