I exactly see it the same as a-pilch, the internet is connecting us globally and with large hubs like CGtrader collecting digital goods of all types and providing it through a search-able user interface allows us to serve the niches in ways unimaginable 10 years ago. If there are just few people in the world that would like your stuff then those few will find your stuff.
You can basically experiment freely to see what kicks in and what not and just go wild on the creative side and create the things you love to create.
The ideas on how to make it in a product and market it basically flow alongside that creative process, questions like how could it be used, what can be done with it, etc.? If you can transmit some of those ideas then you basically create a need on the fly as it can trigger some imagination or initiation points for projects.
There are lots of creatives that go for inspiration hunting looking for something but not knowing jet what, just something that can jump start them, to get a vision or direction, a starting point. It can basically be anything, maybe some alien looking rock formations or some strange looking architectures/elements, anything.
You can gradually build up your own specific repository of elements and market it to every new opportunity that arises, like for example the social VR spaces that are coming up soon, etc.
There are infinite design possibility's, basically endless idea space to create in. I would encourage anyone to go and explore that space and keep trying to pull out more interesting stuff all the time, but try to establish what type of stuff one would like to pull out fist. Maybe you like fantasy characters or monsters, or design vehicles, maybe space ships, motion graphics, abstract forms or machine parts, or robots, etc.
It basically does not matter, there always would be someone that can use it, but the important part is that it needs to be of a certain quality, so as an artist one needs to take time and invest effort to grow and get to that level where he starts getting sales.