I will be doing a three tier cake for a birthday party. It will be a simple round cake covered in fondant with stripes on one tier, stars on one, and music notes on the third. I was wondering what the best sizes would be for this. It will need to feed 60 people. I know they usually say four inches between each tier, but that would be way more cake than they need. I dont want the tiers to be too close in size so that it doesn't look right either. Any advice on the sizes to use would be helpful.

You can do a 6-8-10 but put them off centered so they have a bigger "ledge' on one side and a smaller ledge on the other. You can use the smaller edge on the back.
Similar to this mermaid cake, the front of the cake has more room than the back of the cake.

Ok, there are a bunch of people reading this but no body is offering any information. Any suggestions would be greatly appreciated. Thanks!

I would do 6-9-12 and use a 9" styrofoam dummy for the middle tier, if you're really set on making 3 tiers. According to this chart from CC, the 6" and 12" will serve 12+56=68: http://www.cakecentral.com/article14-Cake-Baking-Cutting--Serving-Guide---2-in-Deep-Pans.html

Or maybe a 6-8-10 all in cake like Cakequeen suggested.

The lady that wants the cake is set on having three layers, and wants them all cake.