Floors & Black #1608
 Wall  CC 0

Floors-Tiles. CC0 License.

Source Unknow

 More Textures
Dirty Old Black Shirt #853
 Dark  CC BY-SA 3.0

Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!

Source Paul Reulat

Flowery pattern 3 (colour 2) #2329
 Pink  CC 0

Adapted from a jpg on Pixabay.

Source Firkin

Dotnoise Light Grey #308
 Wall  CC BY-SA 3.0

Sort of like the back of a wooden board. Light, subtle, and stylish, just the way we like it!

Source Nikolalek

Background pattern 328 (colour 3) #1799
 Noise  CC 0

To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i

Source Firkin

Page ornament 22 #2358
 Dark  CC 0

From a drawing in 'A Rolling Stone. A tale of wrongs and revenge', John Hartley, 1878.

Source Firkin

Prismatic Groovy Concentric Background [email protected] #462
 Noise  CC 0

Prismatic Groovy Concentric Background 4

Source GDJ

[email protected] #325
 Grid  CC BY-SA 3.0

Sometimes simple really is what you need, and this could fit you well.

Source Factorio.us Collective

Leaded glass background #2049
 Colorful  CC 0

Seamless pattern the tile.

Source Firkin

Checkered [email protected] #323
 Grid  CC BY-SA 3.0

Simple gray checkered lines, in light tones.

Source Radosław Rzepecki

Background pattern 308 (colour 5) #1869
 Blue  CC 0

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

Source Firkin

Background pattern 227 (colour 5) #2310
 Colorful  CC 0

A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.

Source Firkin

Simple Horizontal Light #982
 Light  CC BY-SA 3.0

Sometimes you just need the simplest thing.

Source Fabricio

Stone Wall & Dark #1538
 Stone  CC 0

Incoming catena. Stone & well. CC0 texture.

Source Unknow

Zig-zag pattern 2 #2417
 Grid  CC 0

A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.

Source Firkin

[email protected] #754
 Light  CC BY-SA 3.0

This is so subtle you need to bring your magnifier!

Source Carlos Valdez

Fabric pattern (colour 4) #2399
 Fabric  CC 0

Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

Triangles #743
 Grid  CC BY-SA 3.0

Sharp but soft triangles in light shades of gray.

Source Pixeden

Tessellation 16 (colour 3) #2213
 Green  CC 0

The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.

Source Firkin

Light [email protected] #760
 Paper  CC BY-SA 3.0

Has nothing to do with toast, but it’s nice and subtle.

Source Pippin Lee

Wavy background #2020
 Green  CC 0

CC0 and a seamless pattern from a tile drawn in Paint.net .

Source SliverKnight

Melty & Red #1665
 Metal  CC 0

Misc. CC0 License.

Source Unknow

Seamless Canvas (Pale Brown) #1165
 Fabric  CC BY-SA 3.0

A seamless canvas texture for using as background on websites. Colored in pale tones of brown.

Source V. Hartikainen

White Wave #681
 Stripes  CC BY-SA 3.0

Light and tiny, just the way you like it.

Source Rohit Arun Rao

Seamless tile 4 #1812
 Red  CC 0

Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern

Source Firkin

Prismatic Dots Background 2 #503
 Noise  CC 0

Prismatic Dots Background 2

Source GDJ

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

Prismatic Dots Background [email protected] #506
 Noise  CC 0

Prismatic Dots Background 3

Source GDJ

Billie Holiday #1002
 Light  CC BY-SA 3.0

No relation to the band, but damn it’s subtle!

Source Thomas Myrman