Moksha

Technically Kaushalia is correct...as far as USCIS is concerned they only need proof of meeting within two years of filing. With that said, all of the documentation that you send to USCIS goes to the Delhi consulate and they will see it prior to the interview. My husband (then fiance) and I submitted a lot of proof of relationship with out USCIS petition, and although I can't say that it helped I know it didn't hurt. I kind of went with the theory that we would submit proof of the relationship up to the point of filing in the USCIS petition stage, and then submit proof of relationship from the filing date to "present" to VFS. That way, when the Consulate looked back on your file they would have a snapshot of your whole relationship.
Delhi is a tough Consulate, and doesn't go own one clear path, so go with the "more is better" theory...I've never heard of USCIS sending petitions back too much proof. I have heard of Delhi denying for not enough. As for the engagement pictures, I would think as long as they are not elaborate I would send them. We didn't have an engagement ceremony so we sent a letter explaining that.
I also suggest, and I know I'm a bit ahead of where you are, that you take another trip over there for the interview. Again, Delhi being a high fraud Consulate, you being there for the interview could potentially make a difference. I only say this now so that it will give you some time to maybe plan for it. Plenty of people have gotten approved with their SO not being there for the interview so it's just something to think of.
~Jen