A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A free seamless background texture of "timber wall" (colored in dark brown).
Source V. Hartikainen
The image is a remix of "edo pattern-samekomon".I changed the color of dots from black to white and added BG in light-yellow.
Source Yamachem
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Polyskelion Pattern No Background
Source GDJ
Nothing like a clean set of bed sheets, huh?
Source Badhon Ebrahim
A free seamless background texture that looks like a brown stone wall.
Source V. Hartikainen
The image depicts the Japanese Edo pattern called "seigaiha" or "青海波" meaning "blue -sea- wave".I hope it's suitable for the summer season.
Source Yamachem
The classic notebook paper with horizontal stripes.
Source Are Sundnes
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
Remixed from a drawing in 'A Girl in Ten Thousand', Elizabeth Meade, 1896.
Source Firkin
A pattern derived from part of a fractal rendering in Paint.net.
Source Firkin
Prismatic Triangular Seamless Pattern III With Background
Source GDJ
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A comeback for you: the popular Escheresque, now in black.
Source Patten
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin