Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
From a drawing in 'Two Women in the Klondike', Mary Hitchcock, 1899.
Source Firkin
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
You know you love wood patterns, so here’s one more.
Source Richard Tabor
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
Free tiled background with colorful stripes and white splatter.
Source V. Hartikainen
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
A repeating background with a look of paper. I have added some changes to PatCreator. Now you can share your designs by submitting them to a new gallery section. Start by clicking Edit with PatCreator above.
Source V. Hartikainen
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Remixed from a vector adapted from a jpg on Pixabay. The tile this is constructed from can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
From a drawing in 'La Principauté de Liège et les Pays-Bas au XVIe siècle', Société des Bibliophiles Liégeois ,1887.
Source Firkin
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
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
Might not be super subtle, but quite original in its form.
Source Alex Smith
Prismatic Polka Dots 3 No Background
Source GDJ
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin