New i580:can I use my own pics as wallpapers?

I have a motorola i580 and it dosen't give me the option of using the pictures saved to my memory card as wallpapers why? Do I need to resize them or name them a certain way,or does the phone need an unlock code of somekind to allow this? Anyone else here have this problem?

Unless the pics are taken with the phone, they cant be used as wallpaper or caller id. I don't know why.

That's most likely so you spend money on purchasing wall papers, although you can use them because when using a certain software program you upload wall papers.