Image size limit is 4mb per photo. We do this for a few reasons: 1) Image quality is limited by the Internet, computers, bandwidth etc. 2) We want to make sure that you don't have to spend too much time uploading photos. 3) It is important to make sure that we keep the system working fast so it doesn't make sense to put too many resources into resizing photos.
We recommend that you choose one of the lower settings on your camera. If you don't have the manual for your camera don't worry, just about every camera has a manual online. Do a Google search for "how to adjust image size for [insert camera make/model name here].