The possibilities are endless when decorating cakes. It sounds like you're making a fancier cake. I've never done anything fancy, but can throw out some general ideas that may (or may not) help
Well, you could use dark chocolate and drizzle over. Take a saucepan and fill with some water, and put this over a medium flame. In a separate bowl, put the chocolate (broken into small pieces) and put this bowl into the saucepan. Stir with a spatula to melt. You could consider adding a little heavy cream to the bowl to make the melted chocolate less thick. Use good chocolate with no hydrogenated oil.
If you bake a cake and frost it, you can use chocolate chips, M&Ms, or various other candies to create a border around the top of the cake. If you check the baking section of your local grocery store, they should have an assortment of candies, sprinkles, etc. that you could use for topping. You should also find these frosting tubes + decorative tips, which will allow you to create a fancier border.
There is edible gold shimmer. You could also get dragees or pearls for decorating, but I don't know how safe it is to consume the dragees with actual metal. You can use non-metallic sugar pearls, though.
Check out the following link...
Edible Dragees > Edible Pearls at Fancy Flours
If you go to the following link, you can find gum paste flowers, which could make your cake look fancy...
Gum Paste Flowers for Cake Decorating
Another idea to making a fancier cake is to simply use a different type of baking pan. That way the cake itself will have a unique shape instead of the typical square or round pan.
Aside from that, you can type in "cake decorating tips" into Google and find all kinds of stuff.