Features that improve styling of the frame of the main image:
I would like to offer a use of another element, a"wrap container" so the main image is placed inside it. Using padding to control the size of the frame (the space between the edge of the image and the edge of the wrap container), this element can be styled with gradient, image background and second border or/and second box-shadow... to allow for more interesting design options for the way the frame around the image looks. You can then use seamless wood, paper or metal texture for elegant frames.
I would like to point out the fact that most talented programmers are completely or nearly blind when it comes to having a good design eye. User interface and styling options are both indicators of that. So I would also love to see a user interface that has control over a logical group of options in one place instead of all over... for example: Border Style for main image (size, color, corner radius) and for thumbnails (all 3 pointer states) could be on the same page. I guess because there are Lite and Pro versions: the premium features or options in Lite version can be "grayed out" and serve as a teaser.