I think that the best way to attract ECAs is by allowing them to connect (meaning to contact ECA by phone or email) so that they can tell them how good it is to become a vendor on TC. If you are an ECA then you can share your own success story but if you have good connections with ECAs that you purchase every month from then you can collect their email addresses and give it to others.
The best way to get first hand info is from ECA's themselves.