Tessellation 16 (colour 4) #2212
 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

 More Textures
Background pattern 24 #198
 Dark  CC 0

The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.

Source Firkin

Stripy checkerboard pattern 2 #1767
 Dark  CC 0

Simple combination of stripy squares with their negatively coloured counterparts

Source Firkin

Dark Circles #306
 Dark  CC BY-SA 3.0

People seem to enjoy dark patterns, so here is one with some circles.

Source Atle Mo

Checkered Light Emboss #280
 Grid  CC BY-SA 3.0

Sort of like the Photoshop transparent background, but better!

Source Alex Parker

Graphy #350
 Grid  CC BY-SA 3.0

Looks like a technical drawing board: small squares forming a nice grid.

Source We Are Pixel8

Background pattern 250 (colour 3) #2169
 Colorful  CC 0

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

Source Firkin

Background pattern 223 #2353
 Red  CC 0

Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.

Source Firkin

fawn spot pattern #2472
 Dark  CC 0

The image depicts a Japanese Edo pattern called "kanoko or 鹿の子" meaning "fawn" which has a fur with small white spots.

Source Yamachem

Background pattern 306 (colour 4) #1877
 Colorful  CC 0

Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.

Source Firkin

Diamond pattern (colour 9) #2269
 Fabric  CC 0

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

Source Firkin

Grilled Noise #581
 Fabric  CC BY-SA 3.0

You could get a bit dizzy from this one, but it might come in handy.

Source Dertig Media

Background pattern 223 (colour 3) #2351
 Green  CC 0

Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.

Source Firkin

Prismatic Groovy Concentric Background 4 #461
 Noise  CC 0

Prismatic Groovy Concentric Background 4

Source GDJ