To add , its not bad at all with what you used for sure.It really is in what you use to make it pretty, some things are expensive but wow its like night and day with what you could do.I am glad you posted pictures , its very cool!
clay is funny at times but if you think like a carpenter you will surprised.Or get epoxy , that stuff is fun.Or layer a light coat of clay on the foam you have would look like stone.
But for reals it looks cool