On etsy they have a place where you can post promotions and it is free. I have found that it works as well or better than the showcases. I have never been in a treasury so I can't comment on that.
All you have to do is go to community, forums, and under forums scroll down to promotions. I have been posting our team on there as often as I can. You can either add to the post or create your own.
I have also posted on other promotions, and have created my own posts. I believe it helps in traffic to your site.This is the link to the promotion I have made
This is the link to the promotion main page:
The idea is to keep the post going to the beginning of the list.Try it, maybe it will helpKaren