Scope of work contents in freelance development

Question

One of my clients demanded to append screen shots of UI in the SOW. Also, I was asked to give a workflow diagram for the same. The project I am about to take is relatively small and my question is,

• Should we always provide UI snap shots before project begins? (at least basic). Personally I feel this is not possible as UI keeps changing until agreed upon by client, which is waste of time before development.
• Is it necessary to provide both Data Flow Diagram (DFD) and UI screen shot before development begins?