How to grow Merch account

Hi experts and seniors here, I am approved for Amazon Merch and I have been trying to find how I can upload more images and set the preview image differently. I understand this is not possible for Merch sellers. FBA seller are able to do at this point but I am unable to sign up as one and provide the printing service.

Wonder if anyone can share some workarounds for this. Currently, I am thinking of setting up a landing page of my brand where everyone is able to see how the t shirts will look on models, front and back, then linking them to the amazon link for purchase.

Greatly appreciate any insight.

You don't need fancy mock up to sell on Amazon Merch. Just focus on quantity over quality here. Try cross niche ideas (Trendy+Evergreen).
You should be able to make some decent sales. Goodluck.

Thank you very much for the advice and taking your time

how you did to get approuved ?