Trades to show off eacothers work Use other peoples items as part of the product picture and link to their store in the listing Feature each other on social media
https://www.pinterest.com/TheWaysOfOld/group-promotion-board/ A lot of people use group Pinterest boards. To join a group board you must first follow a board, then get an invitation to pin. This is my group pinterest board. anyone who wants to join, message me your pinterest name and follow my board. Then I can invite you to pin. :) Other than that, teams are the best way to collaborate.
I am willing to send anyone in the group items that I have made if they are willing to display or wear along with your own work. I will do the same on my site. Anyone interested can send me your shipping info in a private message. John