The only thing I can think of for improving engagement is making use of the "tried it" button, I'm hoping to get a bunch of accounts clicking "tried it" on pins from my main account. The only problem with the "tried it"button is you can only click it once per account per pin & you need to write a unique description
I did a small test a clicked tried it on a few of min pins and when I look at my source on pinterest (https://www.pinterest.com/source/yoursite.com), i'm seeing these pins pop up every day. I think having the tried it button clicked allows pinterst to show your pins to more people
i think the next step would be to study the effects of the tried it button when its clicked immediately after pinning, a couple of hours after and a few days after to see if the effects are the same.
One of my problems with pinterest is you need a lot of unique images. I've been uploading the same pictures over and over with no problems, but I think this lowers the chances of other people seeing your pins. I haven't tried it, but im sure posting unique pictures everyday gets more views and more engagement
Basically i think we need to find a way to take advantage of the tried it button and some way to consistently post unique content