A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
Kaleidoscope Prismatic Abstract No Background
Source GDJ
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
A seamless paper background texture colored in pale yellow. This seamless texture is ideal for those who need a yellow background image for their website. The texture resembles paper.
Source V. Hartikainen
The classic notebook paper with horizontal stripes.
Source Are Sundnes
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Background pattern originally a PNG drawn in Paint.net
Source Firkin
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
Prismatic Abstract Line Art Pattern Background
Source GDJ
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Inspired by this, I came up with this pattern. Madness!
Source Atle Mo
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin