I think it's great idea. I would at least try it. I'm not really a T-shirt person but I know many who wear them and I think some would be interested in something like this.
I like your landing page as potential wearing customer, but I don't think it would attract me to advertise with you. I would only change the pictures representing what kind of pictures people upload. Here you can't see that person wears T-shirt on an event or in a day in their life, you only see T-shirt and don't get the feeling person is wering it outside of their bedroom.
I think that feature of choosing what brand will you promote with this T-shirt is important. You can see that many commenters saw this as a problem.
But I think that here is a problem from the side of companies who would advertise on your T-shirts as well. If I used your service for promotional purposes, I would like to know that in front side of T-shirt there would not be something opposite of what I would like my brand to be. But I think that for starters you can filter that out manually.
This sounds interesting to me. Where and how did you gather feedback on your idea?
Please contact me, jasna at hekovnik.si when you have landing page up or will be able to sign up.
The video made me install the app on my Iphone. And I like your app represented on white iphone better than on black (as seen on your landing page)
But I'm not a designer so I didn't have any expectations from article or video. It was just fun and nice teaser for app for me.