1. Can't help you with this one...Why would you want that?
2. Label them as such. You can set up a filter that does this for you if you'd like. First, click "create a filter" (next to the search the web button), then in the "has the words:" field, type this: "filename:jpg OR filename:gif" and keep adding more based on what type of photos you send. Next, check off "has attachent" and click next. Finally, tell it to apply a label of your choosing. You can also have it apply the label to any email that matches that search in your account already.