When it comes to choosing the right cake shape, it is imperative to keep your wedding style in mind.
Here are the most common cake shapes and decorating tips recommended by
http://www.theknot.com.au/
Round
While some might think the shape a little plain, the simplicity of a round cake provides the perfect backdrop for interesting textures and colours.
TIPS - There's no need to hold back on decor with a round cake. Stunning ideas: an allover quilted or pleated pattern; embossed fondant in the shape of your wedding day motif or monogram; or a colorful cascade of sugar flowers.
Square
A square cake is the modern alternative to a round cake - perfect for couples looking for something different but not too over-the-top.
TIPS - Play up the shape as little or as much as you want. Soften the hard edges with elegant touches like sugar flowers, pastel colours and paper-thin embellishments. Or, emphasise the shape by outlining each tier in ribbon.
Petal
Often referred to as ‘scalloped,’ this shape has a flowerlike appearance. Play up the petal shape for a garden wedding, or use the shape on the bottom tier of a round cake to add interest.
TIPS - To keep the cake from looking too bold, go light with the add-ons to compliment and draw attention to the unique shape. We love a white-on-white cake with a burst of colourful sugar flowers to top it off.
Hexagonal
This six-sided wonder is the creative answer to a modern square cake. With such a striking appearance, you'll want to keep the adornment clean and simple. The shape itself brings a lot to the table even without any decoration.
TIPS - Outline each tier in buttercream pearls, accent with fresh or sugar paste green cymbidium orchids, or keep it completely free of decor, save an heirloom or flower cake topper.
Topsy-Turvy
This shape has serious attitude. While it's sure to make a bold statement at your wedding, consider the overall style of the day. It's perfect for a funky loft or restaurant, but won't work as well in an elegant ballroom or country club.
TIPS - Stray from anything traditional like flowers and play up the unique design with plenty of funky add-ons and bold colours. We recommend diamond fondant cut-outs in a bold mix of colours.
Source -
http://www.theknot.com.au/wedding-planning/wedding-cakes-flowers/a-guide-to-cake-shapes