The most popular search terms in the PowerPoint arena are those related to backgrounds (sometimes called templates). I always suggest a simple background because it gives the best chance for your audience to see the text or graphics on the slide clearly. But if you want to choose a background that has graphics, a recent slide illustrated why you should avoid backgrounds with lines in them. This presenter chose a background that had diagonal lines in it. When they showed a line graph on this background, one of the background lines ran through the graph and was more prominent that some of the lines on the graph. This made it look like the most important element of the graph when in fact it wasn't part of the data at all. Very confusing for the audience and it leaves your audience wondering what the real point of the graph was. If you do choose to select a graphic background, avoid ones that will interfere with your audience understanding any graphs or diagrams you add to your slides.