Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
The image depicts an edo-era pattern called "same-komon" or "鮫小紋"which looks like a shark skin.The "same" in Japanese means shark in English.
Source Yamachem
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen
Heavily remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
Dark blue concrete wall with some small dust spots.
Source Atle Mo
A classic dark tile for a bit of vintage darkness.
Source Listvetra
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Dark wooden pattern, given the subtle treatment. based on texture from Cloaks. https://cloaks.deviantart.com
Source Atle Mo
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Here's a seamless brown cork board background texture. Feel free to download or reshare if you like.
Source V. Hartikainen
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
A free seamless background pattern for use on websites.
Source V. Hartikainen
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
This background pattern looks like bamboo to me. Feel free to download it for your website (for your blog perhaps?).
Source V. Hartikainen
Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
If you’re sick of the fancy 3D, grunge and noisy patterns, take a look at this flat 2D brick wall.
Source Listvetra
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo