If you insert a lot of pictures into PowerPoint slides, you're going to love the new layout placeholders in PowerPoint 2007 and later.

If you must use a photo, try to position it on the edges of the slide or in a footer (see below), where it is less likely to conflict with text. You can choose a background in the start wizard, or by ...

To insert a single image across the entire table instead of one in each cell, insert the image into the slide and drag the table over it. Remove the cells' background color, using the "Shading" menu.