For this purpose, you can use text box feature. First copy the image. Now go to insert > drawing & paste the image on the page. Select text tool & drag the text box to wherever want to do the same. Now type something for caption etc. Select the blue save & close. read more
Right click on the slide (non text area) and when the menu pops up click on change background and click on insert image. From there you can click on a small check box (in the bottom-right hand corner) to change the the background on all the slides. read more