First let me say that this app is great. Nokia needs more apps like this one. I think the following two suggestions would improve the using experience of Photo Browser.
1. While browsing in the single-image view, when you start scrolling with your finger the "previous" and "next" images suddenly appear inside of the screen borders left and right. This makes the application look slaggy.
Two possible solutions:
a) Make the "previous" and "next" images appear outside of the screen borders; they can then scroll into the visible area smoothly.
b) Fade the "previous" and "next" images into the screen (during scrolling).
2. While browsing in the single-image view, the scrolling animation stops suddenly once you release your finger. The next image then is suddenly in the center of the screen. This also makes the application look slaggy.
Solution:
Do not stop the scrolling animation once the finger is released. Instead continue the scrolling animation until the next image reaches the center of the screen.