I am about to purchase JuiceBox Pro myself and have the same issue. I'm not sure if your company realizes this but this is a major issue. When we post images online, about half of them are shot in portrait (vertical) format and most of those photos are photos of people.
We just can't use an image display solution that chops off people's heads, faces, and upper body when posting thumbnails of image galleries. That is going to result in very unflattering and hideous-looking thumbnails.
Facebook, for example, has software that "zooms" in on people's faces when creating thumbnails and this would be the ideal solution. I realize this is more complex and i understand if you can't implement that level of sophistication just yet.
At the least can you please offer functionality where for certain images you can specify what part of the image the thumbnail image should cover?
I bet many of your other customers also would appreciate this functionality -- especially when posting photos of people. As it is, all your thumbnails created of people in vertical format photos are zoomed in on their stomach and hip area resulting in awful looking thumbnails.
By the way, the suggestion of "manually" creating thumbnails is really not a practical solution. The whole point of your software is to automate the process when posting dozens of photos and that benefit is completely negated if you have to manually process all the photos taken of people in portrait format.
I'd really need some control over where the thumbnail image zooms in on to purchase this product.