Digitized images are usually specified as a two dimensional array of values, assuming that these values represent colors of an array of square or rectangular pixels. By making appropriate x and y mesh arrays, you could plot such images using the plf function, but the pli command is dramatically faster and more efficient:
pli, z, x0, y0, x1, y1
plots the image with (x0,y0) as the corner nearest z(1,1) and (x1,y1) the corner nearest z(M,N), assuming z is an M by N array of image pixel values. The optional x0, y0, x1, y1 arguments default to 0, 0, M, N.
As of yorick 1.5, z may also be a 3 by M by N array of type char in order to make a true color filled mesh. The first index of z is (red, green, blue), with 0 minimum intensity and 255 maximum.