Ooohhh, that is an awesome idea
My familiar is one of my cats, as well....I think a statue of Bastet is a great idea (or any type of cat statue that really resonates with you...)
Maybe a small box/container that you can put some of your familiar's fur and/or claws in (from when you brush the cat & trim it's claws!!) That would help to centre your familiar's energy there....
Other than that - perhaps a picture of your familiar? I would probably spend some quiet time sitting with the cat, and communicate with it telepathically, and see what the cat "tells you" it would like...
Let me know how it turns out - I think it's a great idea - maybe I'll try it, as well