ElisabethJeannie

Yes for the photos, this is what we did, a regular scan of fronts and backs (including signature), one PDF page / file per person.
 
You still have the ability to upload one if you wish in the upload section, although it's not required.
We did not upload a cover letter and I would say it depends on what you already uploaded. We had bank statements, phone and electricity bills...we were confident enough we did not have to explain or prove anything.
 
Hope that helps!

You don't need this form when applying online, there will be a payment page where you can use your credit card (we used our Canadian one).
 
For photos, a PDF file is good, this is the format we used for all the documents we provided.
 
Good luck !