Might not be super subtle, but quite original in its form.
Source Alex Smith
The classic notebook paper with horizontal stripes.
Source Are Sundnes
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
Prismatic Groovy Concentric Background 5
Source GDJ
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
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
From a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
ZeroCC tileable beechwood wood texture, generated in Neo Texture Edit by me. CC0
Source Sojan Janso
All good things come in threes, so I give you the third in my little concrete wall series.
Source Atle Mo
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
We have some linen patterns here, but none that are stressed. Until now.
Source Jordan Pittman
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Number 1 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Super detailed 16×16 tile that forms a beautiful pattern of straws.
Source Pavel
Seamless pattern the basic tile for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Inspired by a drawing seen in 'City of Liverpool', James Picton, 1883.
Source Firkin
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
Prismatic Abstract Geometric Background 5 No Black
Source GDJ