At the very least you will need an Osceola County business license and a registration with the Florida Department of Revenue so that you can collect and remit sales tax. The license office can advise you of any other requirements, such as licensing requirements for any municipalities or other counties in which you may want to do business. You may also find that you will need to have your business license before a bank will open a commercial account for you. There may also be requirements to advertise any fictitious names, such as Rebel Graphics, you will be using unless you have incorporated your business in Florida.
Once you have done those things, you will also need to check on county and municipal requirements for pulling permits needed to do any installs other than on vehicles.
Good luck with your new business.