How to change the lock pictures on the samsung solstice?

I got a new samsung solstice and every time it locks or unlocks there are about 8 different pictures that show up. Is there a way to change or delete the pictures that show up. i would like to have the pictures that i have taken to show up instead of the phones default ones. Also can i download apps and put on the phone via pc and usb cable instead of 3g.|||it's call screensaver, you can create new screenshot using a custom tool on www.samsung-solstice.com