This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
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
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
The image depicts meshed silhouettes of various things.The original image is an OCAL clipart called "Enter FOSSASIA 2016 #IoT T-shirt Design Contest" uploaded by "openclipart".Thanks.
Source Yamachem
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Background formed from the original with an emboss effect
Source GDJ
Free tiled background with colorful stripes and white splatter.
Source V. Hartikainen
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
Prismatic 3D Isometric Tessellation Pattern 6
Source GDJ