The important is to understand what you prefer to see.
Arts or landscapes? One week is too a short period for a complete visit, so, obviously, you have to decide what you want to see.
All the towns that have been named here are nice, and, moreover (with my great disappointment as milanese
) I must agree that Milano is not the best town you can see in Italy: Milano has only trhree monuments really great: The Castle, The Duomo, and the Last Supper by Leonardo. But, in front of Venice, for example, it's nothing.
For Art, beginning from Rome, see Florence an Venice. I can adsure you that for each of them a week is really too a little period. But I sincerely think that they are absolutely unique.
Milano is a nice play to stay in, and leave for seeing other places: in maximum two hours you can be on lakes, on high mountains, on the sea, on the rivers...wherever you like.
For lanscapes.....sea, country or mountains? If you pass by Venice, instead of Como lake, try Garda lake: it's bigger, wilder and more impressive than Como's one, and it's very close to Trentino, with its mountains.
When you know the exact dates of your trip, write me, and, if you pass in Milano, I'll be happy to meet you.