Hi Adam, I have seen an issue like this before and here is what I believe to be happening.
I suspect you aren't using the same photo for testing between the designer and studio box. I would guess the photo you are testing with on Designer is a photo with an alpha (such as .PNG or .TGA); whereas the photo they are using on studio has no alpha such as a .JPG. I've seen cases where if the photo has no alpha then XPression will fill the border with Black instead of Transparency. To resolve this, I usually set the alpha on the Published Quad to 99.9% instead of 100%. This forces the object to have some transparency and use a transparent border.
Give it a try and let us know the results.
#XPression