This are the most searched keywords ordered by the number of 3D models they already have.
Here you can find categories with a good amount of searches,
good niches to start uploading models to. You want to look for
keywords on the left bottom corner and the smallest bubble as
they are the ones with the top position (left), more evergreen (bottom)
and least amount of models (little bubble).
If nothing convinces you, search on the least number of models page