What if the hostess put a note in with the invitations that basically said, "Since the parents have to fly back home after the shower, I was thinking people might want to send their gifts directly to the couple's house, and then at the shower give them a photo of the item, or some other 'flat,' easily-transportable item. Or, if you want to bring a larger item to the shower, I would be happy to collect them in a box and ship it to the couple's house."
Okay, that is not elegant wording
but this is the sort of logistical issue I as a guest just wouldn't think about, and I'd be the person bringing them a blender and then feeling awkward. If it's a shower I think it's okay to assume a gift of some kind will be brought, and I think the wording above covers most contingencies--gift card/cash, store-bought item that can be shipped, something the guest really wants to give in person.
Also, the only time I've seen people give just pictures of items before is when something has gone wrong--like the item turned out to be backordered and wasn't available in time to give at the shower, so sometimes it's a bit awkward. A note like this in the invitation would tell people hey, this is okay, lots of people are going to do it, so don't feel weird about it.
Maybe the hostess could get an instant camera or set up a way to quickly print photos, and one of the activities could be making simple scrapbook pages with pictures of the items--either pictures people brought, or instantly-printed ones of the larger items (plus other instant shots from the party). That would make it a little more interesting and festive.