Background pattern 223 (colour 5) #2349
 Blue  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

 More Textures
WaveCut #75
 Light  CC BY-SA 3.0

If you like it a bit trippy, this wave pattern might be for you.

Source Ian Soper

Prismatic Groovy Concentric Background 4 #461
 Noise  CC 0

Prismatic Groovy Concentric Background 4

Source GDJ

Decorative divider 229 #2151
 Dark  CC 0

From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.

Source Firkin

Background pattern 291 #1931
 Dark  CC 0

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

Source Firkin

Prismatic Polyskelion Pattern No Background #394
 Light  CC 0

Prismatic Polyskelion Pattern No Background

Source GDJ

Colorful Floral Background 2@2X #488
 Dark  CC 0

Colorful Floral Background 2

Source GDJ

Prismatic Isometric Cube Wireframe Pattern No Background@2X #500
 Light  CC 0

Prismatic Isometric Cube Wireframe Pattern No Background

Source GDJ

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

Prismatic Dots Background 4

Source GDJ

Prismatic Basic Pattern 2 No Background #447
 Noise  CC 0

Prismatic Basic Pattern 2 No Background

Source GDJ

Green Gobbler #85
 Dark  CC BY-SA 3.0

Luxurious looking pattern (for a T-shirt maybe?) with a hint of green.

Source Simon Meek

Prismatic Snowflakes Pattern No Background #411
 Light  CC 0

Prismatic Snowflakes Pattern No Background

Source GDJ