When you put together a new presentation, paying some attention to the background is very important. I’ve seen a lot of presentations where the background is either distracting or making the text on the presentation difficult to read. In the worst cases, the background was overwhelming and tiring.
Imagine sitting in on a very interesting presentation but with every slide your eyes get more and more tired because the background is making it so difficult to follow what is going on and you have to strain your eyes and your mind.
The same that applies to animation, applies to background: keep it simple, functional and supportive of your message. In the case of your background, fit it in with your branding, if you use branding, but in an understated way. The message is more important than your organisation or company logo.
Here too, realise that, unlike on a web page, the person sitting through the presentation can’t do anything to make it your presentation fit the way they want to see it. Take your audience’s needs into account wherever you can.