The advocates of virtual reality often quote "show me your virtual reality system, and I will want to know how I can add to it". I feel the same about multimedia.
If DTP can be described as mixing text and graphics on a page, multimedia involves organising text, graphics, sound, animations, video and other data on a page. However, it is the way that different pages can be linked to allow a variety of routes through the material that makes multimedia a more dynamic, interactive medium for students to work with.
In the past, as an ICT specialist, I have had students put together multimedia projects that included compilations of geographical facts about a specific area, local culture and crafts, simple adventure games and modern foreign languge teaching aids. This list is not exhaustive, by any stretch of the imagination. Multimedia diaries and joke books are just two of a multitude of other possibilities that might be less appropriate for an EFL class .
Again, how you handle this would largely depend on the ability, background and location of your students. A seriously academic geographical database might be less appropriate than a tongue-in-cheek "tourist guide". The cost in time taken to develop a good multimedia presentation is immense when compared to how long it takes to demonstrate the skills needed to knock a few frames together., The skills necessary to do the job well involve at least some background in applying the design process to the task in hand. If they have never come across such a concept before, that too will need to be covered creatively.
Interactivity is another key concept that you will have to consider. Are you more interested in developing your students' oral presentation skills, so that in effect, they are really going to produce some nice rolling slide shows for them to formally present to the class as a lecture with notes? Or do you want them to produce something that is free standing; that others can explore without needing additional input or explanation from the author?
Your choice of software will also influence your approach to multimedia projects. and vice versa. Microsoft PowerPoint lends itself to developing slideshows (although the interactivity features are worth investigating). HyperStudio and similar packages allow much more flexibility for constructing true multimedia.
Multimedia can have impressive results. The best projects I have seen though have taken my students a great deal of time to develop.