For a BlackBerry you can make themes. You can either get free ones that are okay, or you can pay a few bucks for some pretty cool ones. I downloaded one the other day to make my BB look like an iPhone. Anyways, two days ago I downloaded a computer program that allows you to make your own personal themes. I made one pretty quickly, and by quickly I mean little thought went into it but a lot of time. I plan to make an all Simpsons theme with a different Simpsons character for every icon, and a Kidrobot theme for Aubreys BB. Here is the one I made just tinkering around with the program, without reading the multiple PDF instruction pages.(Notice that I changed my BB browser icon to an icon that looks like Mozilla FireFox but it is actually Tails from Sonic.)
First picture you can see how lame and generic the icons are. They are the general ones that come one the phone. They have the large blocks and you can not see the background between or under them.
For the following two pictures you can see how I changed the icons with just googled images. But now the icons are die-cast cut to where you can see the background behind them, and between them. I can do much more stuff, to completely personalize my phone; time invested.