I normally wouldn't help somebody with anything to do with WM but I'll make an exception.
You can't resize icons in Launcher Pro, just widgets. Although you go through the widgets menu to create the icon, it is still technically not a widget.
So, you won't be able to enlarge them without first removing them and starting over. Long press the home screen to bring up the menu and select widgets, and you should have 4 choices for Desktop Visualizer, (Large, Middle, Small SS, and Small. Just choose which size you want, follow the steps, and then create your icon.