How do you make a background like this?

Collage Makers:

Picture2Life is a powerful, but simple and easy-to-use online image editor which also allows you to create collages and animated gif’s (or animations): http://www.picture2life.com/Tour/Default.aspx
http://www.dundoo.com/create.php (Collage Album Maker)
http://www.makeuseof.com/dir/hockneyizer-photo-collage-generator/ ( Photo Collage Generator)
http://www.megacollage.com/index.html (The best compilations of popular media including custom photo collages, music and video playlists and text compilations.)
How to Make a Picture Collage in Photoshop: http://www.ehow.com/how_2085591_make-collage-photoshop.html

Collages from your photos as wallpaper and print: http://www.photovisi.com/
How to make a collage of your favorite photos for your desktop using Picasa: http://www.googletutor.com/2008/07/21/how-to-make-a-collage-of-your-favorite-photos-for-your-desktop-using-picasa/

Ron
References :

Wanna make a collage of pictures, you can have a try for "photo collage studio", which i have used for a long time, and it always works great~~

This smart program provides us lots of collage background and scrapbook templates, you just need add the photos into the layouts and picutures will be combined into togeter side by side.. Different layouts decide the photo numbers you can put into!
References :
http://www.photo-collage-software.com?page=173