A light gray wall or floor (you decide) of concrete.
Source Atle Mo
This light yellow background pattern consists of an irregular pattern of spots. Here's a light background pattern with yellowish tint.
Source V. Hartikainen
Zero CC tileable wood texture, made by me procedurally in Neo Texture Edit.
Source Sojan Janso
Prismatic Abstract Geometric Background 5
Source GDJ
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Geometric triangles seem to be quite hot these days.
Source Pixeden
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Prismatic Groovy Concentric Background 5
Source GDJ
Prismatic Polka Dots 3 No Background
Source GDJ
More carbon fiber for your collections. This time in white or semi-dark gray.
Source Badhon Ebrahim
Here's an yet another seamless note paper texture for use as a background on websites.
Source V. Hartikainen
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A seamless pattern made from the gold Penrose triangle by GDJ and the two remixes
Source Firkin
A set of paper filters. The base texture is generated the same way, only the compositing mode is varied.
Source Lazur URH
Prismatic Polka Dots Mark II No Background
Source GDJ
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Dark blue concrete wall with some small dust spots.
Source Atle Mo