The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Have you wondered about how it feels to be buried alive? Here is the pattern for it.
Source Hendrik Lammers
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
This background pattern contains worn out colorful stripes as a texture.
Source V. Hartikainen
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Submitted as a black pattern, I made it light and a few steps more subtle.
Source Andy
Seamless pattern made from a tile that can be obtained in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Prismatic Snowflakes Pattern No Background
Source GDJ
A dark pattern made out of 3×3 circles and a 1px shadow. This works well as a carbon texture or background.
Source Atle Mo
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
A seamless paper background colored in pale yellow.
Source V. Hartikainen
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.