LoversFromAfar

Other than a lot of waiting its fairly innocuous process.  

Boarding passes, entry stamps into country, hotel folios with named occupants are good primary evidence.  
 
I submitted entry stamp and two boarding passes 

Pictures are of little utilitarian value for proof of meeting within the past two years 

There are apps for your phone that will help resize your passport photos to the size that you need for any occasion. After resizing and it is required to send them on to someone to print these apps make it easy.
 
https://www.phonearena.com/news/Best-apps-to-make-quick-passport-visa-and-ID-photos-on-the-cheap_id80517
 
For IPhone
https://www.ikream.com/2019/04/5-best-passport-photos-app-for-iphone-28665
 
For Android
https://thedroidguy.com/2019/03/7-best-passport-photo-apps-android-print-save-money-1073825
 

As long as you are visible and recognizable that should be OK.  I would make sure that you go to the extra effort and get some GOOD, CLEAR photos.
 
If the photo you are sent is a tiff/gif or other LOSSLESS format you can email it.  There are many web sites that will scale the photo to the proper dimensions and then print out.   Also don't let the photographer take the a photo in the wrong background and try and edit it.
 
If USCIS doesn't like it you'll get an RFE for it.  So if you don't want to add another 2-4 weeks to your visa time get some good photos.