Do I need to stick to a certain divider or powers of two in the size of the sprites?

Then still a high probability you are going to glue in satin, so it doesn't matter.
But the Atlas is already under the minimum power of two customize.

And you make the game under some prehistoric console that doesn't support numbers greater than 2^3? Or maybe the game engine can only work with squares? If there is no such restriction, then why not something they adhere to. Draw as nice and comfortable.