The documentation on this is sparse and not that helpful.What I've found through trial and error:To add an image service to a map I add a layerfile that I created previously that points to the image service. You can then manipulate the definition query to select how it's displayed.To add one from scratch I use something like the following, but you won't have control over symbology, etc:
url_ndvi = r"GIS Servers\arcgis on www.sciencebase.gov\phenology\ndvi.ImageServer"
inpoly = r"I:\NPS_NPMP_data\PythonCode\testPhenoTools\Sheldon_Boundaries.shp"
#the inpoly is used to set the extent
#pull our image service data
arcpy.MakeImageServerLayer_management(url_ndvi, "tmp_extract1", inpoly)
#make a arcpy layer from it so that we can manipulate it
imgSvrLayer1 = arcpy.mapping.Layer("tmp_extract1")