Change wallpapers for samsung star

Hello,
Hi Friends, I have bought samsung star s5233. I downloaded wallpaper and when tried applying the wallpaper, the wallpaper is stretched. Since there are 3 desktops in it, either the wallpaper stretches to 3 desktops. I tried reducing the pixels and changing the format. If the wallpaper fits in to one desktop, the other two desktops is empty. Can somebody help me with this?