The weather at the lake is quite umpredictable. Even during summer, in this upper part of the Lake, storms are frequent, usually they come in the late afternoon.
I went in mid June and it was supposed to be hot but I ended up wearing ALL i had in the suitcase!!
Better to bring different layer of clothes so you can adjust as you go. Best are soft and comfortable stuff. Bring good walking shoes. Almost nothing is flat here ;-)
Luggage and bags:
In the case of Riva, either a back pack or rolling luggage would be acceptable. The main section of Riva is well paved so wheels on your suitcase can move freely.
Clothing/Shoes/Weather Gear: We visited in late fall and the weather, although overcast and foggy, was lovely. I'd suggest a weatherproof jacket and an umbrella however, just in case.
Toiletries and Medical Supplies: I'd assume anything you might require is readily acceptable. Perhaps a cold remedy you are familiar with from home...BTW, the Italian travel packs of tissues are wonderful.
Photo Equipment: In the old portion of Riva, I noted at least two shops selling film. One shop sold cameras so I'd assume additional memory would be available. I did NOT see any shops offering digital transfers on to CD, but that is not to say there aren't any.