Is it permitted, to have a piggy bank shape like, well a pig - for example?
First, the permission to paint or sculpt is not related to whether we can eat the animal. Some animals are treated more strictly: humans ,eagle, lion and bull. There are differences between representation in relief (3 dimensions) and flat (2 dimensions), and between whether there is a possibility that idolatry might be involved or not e.g. when the representation is educative.
There are nuances between rishonim regarding some cases.One of the important Tosfot is in Yoma 54ab.
But anyway, the criterion of Kashrut is not mentioned in halacha. For instance, the King Solomon had a throne with sculptures of lions as written in Melachim I. Lion is not Kosher.