Using online images from other websites to create wallpapers...izat a copyright infringement?

HEY, i wanted to set up a website where people can download wallpapers of celebrities or sports stars for free. i was going to create the wallpapers using softwares like photoshop/corel and use images that i find online to turn them into wallpapers. am i allowed to use images from other websites and turn them into wallpapers?? izat against any copyright law? am not going to price any wallpaper, i just wana create wallpapers? HELP thanks