Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
Here's a new gray "fabric" pattern. Use it as backgrounds for websites or for other purposes.
Source V. Hartikainen
The name tells you it has curves. Oh yes, it does!
Source Peter Chon
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Dark Tile-able Grunge Texture. I think this texture can be classified as grunge. It's free and seamless, as always.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
Tweed is back in style – you heard it here first. Also, the @2X version here is great!
Source Simon Leo
A free green background pattern with a pattern of rhombuses on a seamless texture. Feel free to use it as a tiled background image on your web site.
Source V. Hartikainen
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
Did anyone say The Hoff? This pattern is in no way related to Baywatch.
Source Josh Green
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
Luxurious looking pattern (for a T-shirt maybe?) with a hint of green.
Source Simon Meek
Here's a subtle marble-like background for use on websites.
Source V. Hartikainen