If you're fairly comfortable using an IWB, you'll find them easy to create. If not, and you fear it might take you hours to learn how to do that, note that spending hours creating material is something I think you should NOT be doing as a teacher.
Importing images on to an IWB is, however, very easy, and good photos do look great at the sort of size you can get. It would be interesting to be able to discover how much language comes out of an A4-sized photo compared with the same photo occupying half one wall of your classroom. I know which I'd rather have!