You see how to trees take up more than one tile on the map?
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Animal sprites are self-explanatory
I see what you mean by the larger objects. Keeping everything to one tile was done on purpose for the style, so I won't personally be adding anything like that. As for animals, there are over one million species of animals in the world, you really need to narrow it down. If you're wanting a cow for your farm and someone makes a squirrel or a kangaroo, that's not going to be very helpful, you know?