If your course addresses topics that the public could use better awareness about (now, or perhaps even historically), consider asking students to first review real issue awareness ads. For added depth, see if students can generate the key elements of an effective ad from those they examine, and together create or contribute to an assessment rubric using this information. Then, in groups or individually, students create their own awareness ad - on an issue of their choice from your course, or one you assign.
Because such ads tend to have limited text, consider also requiring students to attach a reasoned rationale, using course material for support, explaining why they selected the text, tagline(s), and/or images used in their ads.