A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Alternative colour scheme for the original floral pattern.
Source Firkin
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
This is sort of fresh, but still feels a bit old school.
Source Martuchox
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Zero CC tileable hard cover cells book texture, 4k, scanned and made by me. CC0
Source Sojan Janso
An abstract texture of black metal pipes (seamless).
Source V. Hartikainen
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin