Is GIMP the appropriate program to use to create a background for a flash intro to a webpage, or is there something better?

I have a flash template and my own movie that I've converted to .swf, but right now it's just set to show up on a black background. I know I can change the color code in the template, but I'd sort of like my background to be gradient like my main website page and I'd like to have my currently "square" video play inside a shadowed oval-ish shape.

Can someone steer me in the direction of how to accomplish this or direct me to a website that can teach me?