I can't decide if I want to use round cakes or square. I am making a 3 tier cake. the top tier will be a doll made to look like Cinderella the bottom two tiers will be 10" and 12" (can't decide square or round) and 3" high (plus torting and filling). This is for my niece's 5th birthday and the design is completely up to me.

Well, if the cake will be part of her dress, I would go with round for that portion, the bottom tiers could then be round or square, a round top on top of a square looks very good! The two bottom tiers could almost have the appearance of steps opr platforms that the doll is standing upon! If you have petal pans, these are very good for this kind of cake too.
Hugs Squirrelly

I've seen pictures of a doll with both round and square/rectangle (I have a habit/addiction looking at pics of cakes now!). Personally I think the round looks better! But - I am sure whichever one you do - it will look great!!!!!!!!!!!

The lower tiers will NOT be part of the dress.

If the lower tiers are not part of the dress...I think I would use the square pans. But that is just my opinion.

Haha, well I must admit, because I always have used rounds or petals as the bottoms, I like the idea of the square, just for a change for me, so that likely influenced my opinion. It is all good!
Hugs Squirrelly

I would more than likely use the square on the bottoms, as earlier stated by SQ, it would look like steps or platforms!
I might also line the back corners up to widen the look.