All you have to do is take your photo and cut it into even sized pieces! Sounds a bit shaky, but take a look at this scrapbook layout and the close up of the expanded photos.
This method of scrapbooking accomplishes 2 aesthetic issues. First, the photo takes up a lot of space, while keeping the theme and streamline of the layout, without making it look cluttered. Secondly, it makes the photo "appear" to be matted, when it is not. Both of these additions make for a very interesting, eye-catching scrapbook layout page!
Do It Vertically, too!
You can also do this method using vertical photographs! This photo, I cut into 1/2 inch strips and placed them evenly spaced on a contrasting color cardstock matte and then placed that whole ensemble onto the layout. Again, quite an aesthetic eye catcher! Now as for the color of cardstock you use, that is your decision. I didn't use a color from the photo as I thought that would just blend to much and you wouldn't be able to see the continuity of the photo. I chose the blue as that was main color in the other photos - the blue sky - so I stayed with that shade and just used a different hue. The blue I used is soft, suttle and blends very well with the images and colors of the photo. You can still plainly see the full photo but it has the little bit of expression in there. So just pick and choose, trial and error which color cardstock that would look best on your layout.
I would venture to say that expanding photos would be best if kept to scenery or objects, but if you have extras or can make copies, give it a try on any subject. You never know what you might come up with!