Hi Sara,
Do you have PowerPoint presentation software or similar? You can insert pictures into a slide to create a collage, you can rezise the images to make everything fit. I resize by scaling down the percentage ratio to keep everything on proportion. You can even add to the slide... Kinda like making a progress poster.
When you have finished, save the slide as 'jpeg image file'.
This is just an option I have used and I think is a good way to make sure photos are shown in order.
Good luck