Yes, first of all I think that we should go with a plain 2D view. Isometric will be difficult to animate. So all the elements seen from above.
I wonder how cartoonish elements would look like on a 'real' background? Won't it give a nice 3d impression?
I like the pens made by @markusm they are not-entirely-2d and should work nicely.

[edit] but I'm artistically handicapped, so whatever you, artistic people, think is best.