I wanted to give you some thoughts on.
A theme for your book, it could be :
people or animals
if you do pick a theme the advantage is that it will give us a possible direction not forsaking the option of doing anything we desired but it might give the artist working on your book some directions or ideas in the same possibilities as Michelle's blog Following the Masters or DSFDF.
This would give some cohesion to the overhaul look of each book ounce finished.
But not having a theme can also be a total surprise on each page.
So follow your heart and let's have fun.