On the profile page, it would be awesome if the main profile image was clickable and opened in lightbox full size. This is mainly good on mobile when a users profile image is tiny and sometimes needs enlarging to see properly. Some community's have strong social interaction and profile images are fundamental to engagement.
Going one step further you could allow people to upload multiple images one after another and then essentially have a profile album. So when you click and open the main image you then access all previous profile images in the same lightbox. Cool huh!