You just put the Image value as the fifth arguments of the Canvas.line
method :
-- Create an Image instance
local mypattern = canvas.Image("mypattern.png")
-- creates a line from 0,0 to 320,200 using this image as pattern with a width for 50px
canvas:line(0,0, 320, 200, mypattern, 50)
PS: I haven't already tested all drawing functions with Image brush, please give me a feedback if it works correctly 😄