I think shifting the business to making the decorations for others is a bad idea. If you're making enough of them to pay, first, people buying that many will be wanting wholesale prices, secondly, if people see you selling enough to prove there's a market, at least one or two will go into competition with you then start a price war. Having shifted the business over, you would probably be going back to less market share.
Shipping them is another potential pitfall in they are a bit delicate, so they could get there broken, or people claim they're broken, and with your temper, blood pressure spikes and ulcer city.
I think you're better off doing what you are doing now, and if you meet some other cake makers you could offer your decoration in casual conversation. The bigger spread of products allows you to shift your efforts to the market's whims of demand.
