RapidPlan can add images that are in BMP, JPEG, GIF, and PNG format, including the ability to import DXF and ERSI files.

For bmp, jpeg, png and gif images, just go to Primitive Objects, and select Image In the Files of Type drop down menu and you will see the image formats RapidPlan can place on a plan.
For dxf and ersi images, go to Tools, then Import.