That is unfortunate choice, especially since I would think your market would be image creators. Think about it, does any image viewing software (iPhoto, Aperture, Lightroom) do this?  Essentially then unless all my images are exactly the same size (that hasn't occurred in over 20 years but it may some day) then they get randomly center cropped.  Do you understand that this directly works against what most image creators want?  Maybe there are some limitations but other gallery software I use is able to accomplish this.

I don't wish to be overly critical since juice box does so many things well.  However this is something so basic it seem sad that it was not given value.

I think there in lies my issue.  If it is a navigation tool it should show where a user would be navigating to, rather than imply it or do it partially.  Think of a road sign that is only 2/3's complete and the only way you can find out what it is completely is to drive down it.  This sign is no longer aiding in navigation but a hindrance.  If I create a gallery for clients that contains 250 images they essentially have to look at every image full size since there is no smaller version, this in effect makes the thumbnails useless and the navigation pointless. 

As someone who has worked in design for 25 years what was the decision process in cropping the images?  How does it make sense as a design element not to show the entire image as a navigation?  To me it seems the code is dictating the design rather than the other way around.  If I use every well know image browser as my design guide why the decision to do it differently from successful examples?   I can completely accept if there is no way to accomplish that. 

I don't mean to be critical, but it was the first thing someone said to me when I sent them a test gallery.  "Oh the thumbnails are cropped that is weird, why did you do that?"  That was there response so basically I'm asking for them.