I'm looking for the easiest way take multiple images of varying sizes and spread them out across a single frame for a slideshow. I have a hundred or so photos in JPG format and I'd like to have 2 or 3 of them on each slide. I'd like to end up with 30-40 image files of these slides. Any help is appreciated. Thanks. 
Here's an image to help visualize what I'm trying to accomplish 


