It's up to you.
It is better to keep things separate as someone might want the characters and not the dungeon. You could always just have separate download files if you want to keep them on the same page.
As for animations, as long as your instructions are clear and people know what they're getting, then it doesn't matter. Just in your description specify which are animated and which are not.
Not necessarily one .png - just one download with all the wall tiles .png or sprite sheet in it.
And a separate download file for the props etc.
So you'd have a characters.zip / a props.zip and a tiles.zip files - and you can make 3 store listings, or put it all in one and people can choose to download all 3 or choose any 1. If one download is more popular than another it will also give you an idea of what people like the most about your stuff.
