You could try tailoring discussions to those student's hobbies and likes. Students who are reticent most of the time actually tend to me MORE outgoing when discussing a topic they are very interested in. Doing this once or twice may "break the ice" with that student and get them more interested in discussions in general.

Also, some students are just not comfortable in large groups. Perhaps you can try and get them involved through writing reflections or other kinds of solo activities instead.

The important thing is that the media is relevant to the content. Having a cute picture of a ktiten next to a spreadsheet about rainfall in Brazil is distracting and unnecessary. Having information come in on all sensory channels (audio/visual) can help to reinforce concepts without being distracting as long as it is relevant to the content and not just filler. I honestly think we need MORE media, not less, in order to fill those sensory channels. It can't just be arbitrary though, it has to be relevant and it has to be followed up by practical practice.