The area between images in Picture Package is completely dependent upon how many images in what size. But you can see the result of your choice in the print preview before selecting. Otherwise you'd need to create a File, New, and make the canvas (at least 150ppi) 8 x 10 (this leaves a 4th inch width and 1/2 inch no print border which will inclusive of the no print zone of most printers). Now manually bring in the image to size (being sure it's proper resolution) and copy/paste them to fit as best possible in this space with the space of your choosing.

Bob