It definitely is not phone specific. Any picture you take can be made a wallpaper even if you take a picture of a family picture it will still work rather well.
Well, It is not all that tough to get it done Just goto mobcrop.com
You can browse through and upload your picture online, crop them according to your phone's model and finally get it done It is all very obvious once you visit that site!
I have a camera phone and took a picture of my new baby to set as my wallpaper (I'm not one to carry around pictures and I got tired of saying "no I don't have a picture of the baby).
Other than that, I have no way of down loading anything into my phone.
With my phone, I just take a picture and choose to make it my wallpaper. So mine is a photo of a picture of 2 of my dead pals (photos before they died of course) with 2 opened beer cans in front of them.