Do you *have* to include a separate proposal describing what you plan to do?

No. A good contract will always include a scope of work but that criterion does give you a lot of leeway.

Should you include detailed information about the design work, either as a separate proposal (to which you refer), an appendix to your contract or as a detailed list within it?

Probably. The more information you include--the more specific your contract may be--the less likely it is that your client will misinterpret what you intend. Removing misunderstandings is one purpose for having a contract in the first place.

There are many ways to handle this however, from a detailed and highly specific proposal, to a laundry list of everything you might ever do with a check off box to indicate which items are covered. If you do that, though, don't forget to leave space to add notes about details: if. for example is supplying some but not all images, hotographs you want to make sure that number and type are specified...