Mike, from what I've seen, it depends a lot of the Visa Office processing your case. The Visa Office processing my case returns 100% of what is sent, except for the forms, obviously. All the e-mails, cards, letters, pictures, plane tickets, etc, are sent back in all the cases. But I know that many Visa Offices don't give anything back. Just in case, we sent copies.
We organized everything using envelopes, nothing was stapled. One envelope for the e-mails, another one for cards and letters, another one for the forms + documents needed, another one for the Police Clearances, etc... Each envelope was numbered and I also wrote what was inside it. Plus, we wrote a "Cover Letter", explaining what was inside each envelope and the number of it, I also gave some little explanation about the pictures sent, highlighting some of them. For example:
Pictures 1 to 10: First trip together
Pictures 11 to 20: B meets L's family
- Picture 14: B, L and L's family, at S restaurant
Pictures 21 to 30: Engagement
- Picture 25: Engagement ring
Of course each picture had all the informations on their back, such as place, date, people in it, etc, but we decided to give them some help by letting them know where to find everything.
Edit: Documents were sent copies as well, notorized though - while the evidences of the relationship were just regular copies. But no originals, in case they lose it.