Seamless Cardboard Texture #1212
 Cardboard  CC BY-SA 3.0

A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.

Source V. Hartikainen

 More Textures
Prismatic Dots Background 7@2X #514
 Dark  CC 0

Prismatic Dots Background 7

Source GDJ

Starting Diamond Shape@2X #138
 Light  CC 0

Simple blue and line to mix.

Source SliverKnight

Prismatic Geometric Pattern Background No Black #408
 Noise  CC 0

Prismatic Geometric Pattern Background No Black

Source GDJ

Background pattern 251 (colour 2) #2166
 Yellow  CC 0

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

Source Firkin

Prismatic Groovy Concentric Background 3 #457
 Noise  CC 0

Prismatic Groovy Concentric Background 3

Source GDJ

Broken Noise #364
 Dark  CC BY-SA 3.0

Beautiful dark noise pattern with some dust and grunge.

Source Vincent Klaiber

Light Grey Floral Motif #344
 Wall  CC BY-SA 3.0

Lovely light gray floral motif with some subtle shades.

Source GraphicsWall

Bright Multicolored Floral Background #559
 Noise  CC 0

Bright Multicolored Floral Background by Karen Arnold from PDP.

Source GDJ

Triangular Psychosis 3 #235
 Noise  CC 0

A colorful triangular background, variation 3.

Source GDJ

Background pattern 259 (colour 6) #2097
 Blue  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

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

White handmade paper pattern with small bumps.

Source Marquis