What does it say when my best selling stock pictures are like Toilet Roll, Bottle and Restroom Icon?

There's always a demand for diverse people (young & old) in various situations: at work, home, school, play, social settings, with friends & family, at leisure, etc... 

Everyone submits sunsets & flowers, but very few contribute cardboard boxes and soda cans.  Find a niche & fill it. One person's trash could be your best-selling treasure.

Adobe Stock accepts 15-second videos, photographs, illustrations, drawings, icons and Generative AI.

I do mostly Wildlife-, Landscape- and Nature-photography. About half of them are natural and half artistic. Both sell equally well. It depends on who the buyers are and what the buyers are looking for. An Adobe partner selling wall murals is likely to purchase artistic where as a magazine writter is probably looking for natural. 
As far as what you should offer next, all I can say is do your own homework. Buyers are looking for almost everything.