I think a microstock dApp would be very successful on Steemit. We have a huge influx of cool photos and illustrations being posted daily, these could be connected to the microstocks dapp if one chose to, perhaps there could be a check box that you could click if you agree to sell your photo “royalty- free”.
I think this would add great success to Steem because we could see a huge influx of money for work provided by the entire blogging community. Another great part about selling royalty free, non exclusive license, is that the photo can be sold an infinitive amount of times.