Your comments

What if you assign the same glass material to the label?
You can make the body material transparent and then assign an image to the backside of the cover. Should work well for you.
Please send your questions to support@boxshot.com if the support link on site doesn't work for you.

As for your question, you can put a plane object to the floor and assign it the image you like.
You can simply drag and drop your external model to the scene, Boxshot will create external shape object automatically.