Everything you put on your slide should be relevant to the topic of that slide and to your audience. This includes not only the text, but the graphics and backgrounds.
Remember, the point of your presentation is to communicate something clearly. The more irrelevant items you have on your slides, the more it takes attention away from you and the more difficult it is for your audience to mentally sift through the pieces and combine them into a coherent whole, all the while trying to listen to you.
And keep in mind that what is relevant to one audience might not be to another. Does the conservative, older audience really want the loud and naughty video bits that are in the presentation for a younger and wilder crowd?