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

 More Textures
Prismatic Geometric Tessellation Pattern 2 No Background #553
 Noise  CC 0

Prismatic Geometric Tessellation Pattern 2 No Background

Source GDJ

Prismatic Dots Background@2X #502
 Noise  CC 0

Prismatic Dots Background

Source GDJ

Prismatic Triangular Background Design Mark II 5 #406
 Dark  CC 0

Prismatic Triangular Background Design Mark II 5

Source GDJ

Background pattern pink and colours #2032
 Colorful  CC 0

A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.

Source Firkin

Prismatic Hexagonalist Pattern No Background #390
 Light  CC 0

Prismatic Hexagonalist Pattern No Background

Source GDJ

Checkered Pattern@2X #323
 Grid  CC BY-SA 3.0

Simple gray checkered lines, in light tones.

Source Radosław Rzepecki

Pinetree in tortoiseshell(亀甲松) #2538
 Dark  CC 0

The image depicts a seamless pattern of Japanese Edo pattern called "kikkou-matsu" or "亀甲松" meaning " tortoiseshell-pinetree".The real pinetree is like this: https://jp.pinterest.com/pin/500744052301065077/

Source Yamachem

plant pattern 02 #2504
 Unknow  CC 0

The image a seamless pattern derived from a weed which I can't identify.The original weed image is from here:https://jp.pinterest.com/pin/500744052301423641/

Source Yamachem

Fish Pattern Background #233
 Noise  CC 0

From PDP.

Source GDJ

Background pattern 298 #1899
 Dark  CC 0

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

Source Firkin

Background pattern 336 (colour 2) #1720
 Green  CC 0

Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.

Source Firkin

Retro Squares Background 7 #397
 Noise  CC 0

Retro Squares Background 7

Source GDJ

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