python - Insert Raster to MXD using arcpy.mapping (ArcGIS 10)

What i want to do seems simple. But again i can't even find a workaround...

I have got a lot of Raster-files (ESRI-GRID) which i need to insert into a layout mxd-file and then export the map to PDF/JPEG/whatever.

The Final Export in Python is no Problem.
But how do I insert/replace a Raster in the mxd file?
It has to be something like:

fcs = gp.ListRasters("*", "GRID")
for fc in fcs:
    [change Raster (/ Raster Data Source?)]
    arcpy.mapping.ExportToPDF(mxd, "D:\\test.pdf")

I Hope that anybody has an idea :)
Thanks for your help!

Markus

Answer

Here is a script that I used for changing all the sources in a map document from an SDE raster catalogs to raster mosaics. This could hopefully be a good lead for what you are trying to do. Notice that I pre-built the .lyr files and stored them in a specific location. You can use artwork21's method to automatically create .lyr files too instead of prebuilding.

import arcpy
path = u'sample' #Our internal path to the mosaic directory. Removed from this sample.
mxd = arcpy.mapping.MapDocument("CURRENT") #You can also have this go to a specific mxd
print "Updating Aerial Catalogs to Aerial Mosaics..."
for df in arcpy.mapping.ListDataFrames(mxd):
        for refLayer in arcpy.mapping.ListLayers(mxd, "*.AERIAL_*", df):
                year = refLayer.dataSource[-4:] #This is based on our naming convention, AERIAL_YYYY

                print  u'Updating AERIAL_' + year + u' to Mosaic....
                if year == u'1970':
                        year = u'1970_72'
                if year == u'1997':
                        year = u'1995_97'
                name = u'Mosaic_' + year + u'.lyr'
                mosaic = arcpy.mapping.Layer(path + name) #Making a new layer
                arcpy.mapping.InsertLayer(df, refLayer, mosaic, "BEFORE") #Insert the layer in front of the layer I am replacing
                mosaic.visible = refLayer.visible #Copying across all the attributes on the old layer
                mosaic.brightness = refLayer.brightness

                mosaic.contrast = refLayer.contrast
                mosaic.transparency = refLayer.transparency
                mosaic.name = refLayer.name
                arcpy.mapping.RemoveLayer(df, refLayer) #Take out the old raster layer
                print name + u' updated.'
arcpy.RefreshActiveView() #Not needed if you are not working on an open document
arcpy.RefreshTOC() #Not needed if you are not working on an open document
del mxd, df
try:
        del refLayer, year, name, path, mosaic #Do your cleanup properly

except:
        pass
finally:
        print u'All Mosaics updated!'

I have a much more complicated version of this that spiders through a drive and changes -every- mxd on the drive too, if that is needed.