Some type of visual in the room as the participants enter is a good way to signal them that your presentation will be different. It could be an interesting picture or funny quotation on the overhead or PowerPoint screen or a nicely done color flip chart page. You could have helium balloons or colorful airbags lining the walkway into the seating area of your presentation.
Use anything that makes the participants take notice. It will build their anticipation of your presentation.