Ahhhh...marketing, let me pull up my sleeves.
On the front you want to set your tone, the message, with one good size pic or several smaller ones of your cakes with a quick summary of you and your business and how you can provide for the customer. You might want to save the summary until the rest of your brochure is done, usually last, because by then, after working on the rest of the brochure, you have a clearer idea of just how to present your business.
The insides should include more pictures of your work, maybe a very brief history of your background, what you provide, flavorings, how you can help a bride (if doing wedding cakes), etc. The thing to remember is to keep it very short and very simple. When people read brochures and see a lot of text, they automatically get bogged down and start skimming. Always generalize your topics and let the bigger questions, the ones that need more explaining, be asked in person or on the phone.
End with your contact information, hours of operation, phone #, etc. There are many marketing tools you can use. One of the better ones that sets your business apart is customer satisfaction, offer a 100% guarantee. Yes, this is risky, but most of your customers will be satisfied (and should be, backup your work) and they will be more comfortable with you than Joe Smo bakery that does not offer some guarantee. There are many more marketing tricks, so I would do some research on the net under "marketing tools, Unique statements (very important), etc."