I have some suggestions for a market regarding Monero, considering it is a coin and a Blockchain which is pretty much contrary to the desires of the governments of the world which crave for centralization and power over the privacy of their citizens, then I would open a market on whether the volume of Monero would end up increasing or decreasing by the end of the next year, or also whether it's price will be able to break through the threshold of 300$ by the end of 2025, this like that.
I would also suggest to open a market on whether Monero will be explicitly banned by the government of an important country within the EU or the United States by the year 2030; though that would be a very long term bet and I doubt people in your web is up to wait so much time for them to cash out a bet like that. Monero is the kind of project which tries to go all-or-nothing in terms of privacy, so I think it is supposed to have a little bit of more spotlight in betting markets opened to especulate on alternative coins.