Would like to see "sky" as a separate one. And maybe "waterscapes" and "landscapes" could be their own too?

I'd like to see animals broken down into cats&dogs, horses, reptiles&amphibians, marine/aquatic animals&fish, birds, and insects.

A premade background category and if possible have it broken down into subcategories like waterscapes, landscape, Cities and Buildings, Rooms and Interiors, etc'

Hmm... I think that many times I have problem to submit a Buildings pictures.. I cannot decide whether they are objects or places. Or parts of buildings.. such as windows and doors or stairs.

Plants : Flowers, Trees, Grass and macro ?
Macro category is way too general.. you can make a macro of almost anything.. maybe adding Macro into each category?
Animals: adding such as type of animals is a great idea by ~Fobtrix-Stock
Household items, maybe divide into : Kitchen, Living room, Bathroom, Dining room, Corridor (or Hall) .. hmm.