/300/150/b34fc7?r=10&d=true&t=true

/150/150/435eee?r=20&g=true

/:width/:height # default gray

/:width/:height/:color # custom color (hex)

/:width/:height/:color?r=N # rounded corners

/:width/:height/:color?d=true # dotted bg

/:width/:height/:color?g=true # gradient bg

/:width/:height/:color?t=true # add text (dimensions)