Rural/Countryscapes and Scenic would seem mergeable. Still Life and objects, depending on how theya re used, night merge - though i am not sure either title would be all-encompassing, so that might need thought (nothing immediately occurs to me). Medieval and Historical seems to be a subset and a superset. Travel would seem a better fit with Aviation and Transport than Military. And of course there are a number of sub-genres that could merge with fantasy, though i suspect they each get a fair bit of use so a combination might be too may to keep track of.

You could try addng a word to weird, such as bizarre, to try to broaden it (though I am not sure that particular combination would do the job). Left field?