You may use it as is, or modify it as you like.
Source V. Hartikainen
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
This is a hot one. Small, sharp and unique.
Source GraphicsWall
Colour version of the original pattern inspired by the front cover of 'Old and New Paris', Henry Edwards, 1894.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
White circles connecting on a light gray background.
Source Mark Collins
This is the remix of an Openclipart clipart called "Maze" uploaded by "any_ono_mous".Thanks.This is a seamless pattern of a maze.
Source Yamachem
He influenced us all. “Don’t be sad because it’s over. Smile because it happened.”
Source Atle Mo
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Lovely pattern with some good-looking non-random noise lines.
Source Zucx
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Prismatic Abstract Line Art Pattern Background
Source GDJ
Prismatic Polka Dots 3 No Background
Source GDJ
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous