Advice from graphical expert on image quality improvement

Our website is displaying poor quality on the user images, and we want to know what kind of filter and/or other improvements we can do to fix this. The site is [login to view URL] It's not expected that the coder do any active work as of now, but rather advice us on what we can do to get guaranteed improved results. We might later post a new job with the actual integration of the advice for the coder.