Ok, I am probably the last person on earth to not have a cell phone so I am not sure how this works but CoverGirl has free wallpapers available for mobile phones. Here is what it says on the site:
Click on the wallpaper of your choice and drag it to the Mobile Machine on the right side of the page. Enter your mobile number, click Accept, press Send and the wallpaper will be sent to your phone. Regular messaging, airtime and/or data charges may apply and will be charged to your wireless bill or deducted from your prepaid account. Participating carriers: AT&T, Sprint, Verizon, Dobson.
Click here for wallpaper choices