Treat crypto currency and image recognition as tools that can be integrated into the marketplace later. You can build your marketplace now. You can choose a payment processor that already accepts a crypto currency, if that eases your mind. And image recognition is available for free already. Maybe not drag'n'drop easy to integrate yet, but we will get there.
With etherium(crypto), large incumbent networks, AI(visual search) coming, does it make sense to start a niche marketplace which could expand into a big market? (web then phone interface)