Aria wallpaper help...portrait orientation

[xraychick01]

I downloaded some wallpapers online. They are in portrait orientation and I didn't even think of that when I downloaded them. Now when I try to set them as wallpaper, the little green box comes up in landscape mode of course, and it cuts off half of the image. How can I fix this? Do I need to resize the images I downloaded?

Edit: I think I figured it out. Apparently the wallpapers I downloaded weren't of the 640x480 dimensions so they won't work.