This is a personal project I've been working on for quite a while and I'd love to get feedback from some of you.
Essentially it's a mashup of Instagram, custom map styles (Mapbox) and a logo designer (kinda like Squarespace logo).
The biggest challenge has been the server-side rendering of images for previewing and sharing. It also renders print resolution postcards for sending to the Moo.com API.
The second biggest challenge has been creating a super simple user experience so the user doesn't have to 'design' anything. The earlier versions were more like a "Photoshop for Maps", now I like to think it's more of an "Instagram for Maps".
Happy to talk more about it if anyone is interested. It's a little buggy so would appreciate if you could post anywhere you get stuck.