A dark metal plate with an embossed grid pattern and a bit of rust. Here's a dark metal plate texture for use as a tiled background on web pages.
Source V. Hartikainen
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Prismatic Curved Diamond Pattern 7 No Background
Source GDJ
Might not be super subtle, but quite original in its form.
Source Alex Smith
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
Tile available in Inkscape using shift-alt-i on the selected rectangle
Source Firkin
Prismatic Groovy Concentric Background 5
Source GDJ
A black tile-able background with paper-like texture.
Source V. Hartikainen
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Sort of like the back of a wooden board. Light, subtle, and stylish, just the way we like it!
Source Nikolalek
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
A repeating graphic with ancient pattern. I came up with this name/title at last minute, so you may find that there is very little of ancientness in this pattern after all.
Source V. Hartikainen