Could be paper, could be a Polaroid frame – up to you!
Source Chaos
This one looks like a cork panel. Feel free to use it as a tiled background on your blog or website.
Source V. Hartikainen
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
Prismatic Hexagonalism Pattern No Background
Source GDJ
Imagine you zoomed in 1000X on some fabric. But then it turned out to be a skeleton!
Source Angelica
Background Wall, Art Abstract, white Well & CC0 texture.
Source Ractapopulous
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Classic vertical lines, in all its subtlety.
Source Cody L
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
From a drawing in 'A Life Interest', Mrs Alexander, 1888.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Geometric Pattern Background No Black
Source GDJ
A dark gray, sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Colorful Floral Background 3 No Black
Source GDJ
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
Prismatic Snowflakes Pattern 3 No Background
Source GDJ
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin