on the external caller id display, no, you can only select the ones given to you in the phone settings->display settings menu, as for the internal
lcd display, you can select a wallpaper from the ones given to you, or use a picture you've taken with the camera or downloaded off the internet. All you have to do is open the picture file, select options, and then "set as wallpaper" and it should be your wallpaper for the inside
lcd display!