Plot values on .png in GUI

Hi, i want to add some information on a self-created map. For example I draw the motorways of california (or some of then) schematical in Visio. This picture will be exported and later on inserted in a GUI in matlab. I will calculate the usage of the motorways in percent and want to add these information as a layer above the image in the GUI. How can I manage this? I dont want to draw the lines with their original coordinates (like it is done in the mapping toolbox).