Exclusive Paper@2X #24
 Light  CC BY-SA 3.0

Paper pattern with small dust particles and 45-degree strokes.

Source Atle Mo

 More Textures
Background pattern 2 #221
 Noise  CC 0

A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.

Source Firkin

Checkered Pattern@2X #323
 Grid  CC BY-SA 3.0

Simple gray checkered lines, in light tones.

Source Radosław Rzepecki

Smooth Wall@2X #28
 Light  CC BY-SA 3.0

Some rectangles, a bit of dust and grunge, plus a hint of concrete.

Source Atle Mo

Background pattern 314 (colour 5) #1835
 Pink  CC 0

The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Background pattern 104 #561
 Dark  CC 0

Background pattern 104

Source Firkin

Bright Multicolored Floral Background@2X #560
 Noise  CC 0

Bright Multicolored Floral Background by Karen Arnold from PDP.

Source GDJ

Concrete Wall 2 #79
 Wall  CC BY-SA 3.0

A light gray wall or floor (you decide) of concrete.

Source Atle Mo

Little Pluses #73
 Light  CC BY-SA 3.0

Subtle grunge and many little pluses on top.

Source Atle Mo

Graphy #350
 Grid  CC BY-SA 3.0

Looks like a technical drawing board: small squares forming a nice grid.

Source We Are Pixel8

Background pattern 306 (colour 4) #1877
 Colorful  CC 0

Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.

Source Firkin

Background pattern 259 (colour 4) #2131
 Green  CC 0

Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

Decorative divider 188 #2521
 Dark  CC 0

From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.

Source Firkin