Dawood

All evidence submitted to the uscis can be legible photocopies unless an original is specifically requested 

Some have combined and had no problems others have. You choose what is best for you guys.
 
Nathan Smith
1234 Main Street
Chicago, IL 60660
 
USCIS
P.O. Box 660151
Dallas, TX 75266
 
March 22, 2017
 
Re: Statement of Intent to Marry
 
To whom it may concern,
 
I, Nathan Michael Smith became engaged to marry Emma Marie Young on January 18, 2017. I hereby state that I am legally able and willing to marry Emma Marie Young and intend to do so within 90 days of her arrival into the United States using the K-1 Visa.
 
I, Emma Marie Young became engaged to Nathan Michael Smith on January 18, 2017. I hereby state that I am legally able and willing to marry Nathan Michael Smith and intend to do so within 90 days of my arrival into the United States using the K-1 Visa.
 
Should you have any questions regarding this matter, please feel free to contact us.
 
Sincerely,
 
________________________                                            __________________________
[Signature]                                                                             [Signature]
[Type Petitioner’s Full Name]                                             [Type Beneficiary's Full Name]

I did  print like  3 photos in a single bond paper, each of them with a title that included the date and a very short description of the place.
As the other members said, photos are not always required, but  I think it is good to send them  along with the other provatory items that Rob listed before.
 
 

If you are talking about the passport style sized photos those are 2X2
 
If you want to include photographs of the two of you those can be standard 4X6 (doesn’t really matter but I wouldn’t send 8x10 size..) label with person, place & date
 
Proof to submit with the petition can be passport stamps & airline tickets that show you have met within 2 years, any travel you have done together (hotel receipts etc), a few pages of chat records, and photos with family & friends

Yes you use section 8 for things that need an explanation, that doesn't fit the form or items which don't fit the nomenclature of the question.

For questions use this link
For documents check the website for your embassy.

The interview letter lists the documents required.