You are in effect trying to accomplish a “green screen” setup. You may find more information about how to better achieve a high quality shoot if you Google for “green screen tips” et cetera.
I can offer you some tips though, as I have lots of green screen experience.
1. Color of the background. Since you are doing a still shot, it is OK to have a white BG. If you ever wanted to make a movie though, go for a color that you will not be wearing or is a part of you (white is your eyes and teeth, which actually looks really funny when they’re green screened out… transparent face), as the video editing program can remove all that color automatically and give you a pretty decent result.
2. Shadows. Shadows are your number one problem. You want there to be zero shadows cast by you onto the white BG so that the background can be masked out more easily and more successfully. Use whatever lights you have, position and angle them however they need to be to eliminate most shadows while still keeping you looking good and well lit. You can also move yourself and the camera a step away from the screen, but sometimes this will leave your feet “ungreened” and thus they can’t be in the cover. If you wanted a torso shot though, this is perfectly great.
3. Quantity. Take as many shots as you can stand to take. Two hundred, three hundred. Pose, snap a few, and adjust a light a bit. Take more, adjust lights. Rinse, repeat. This is a photography tip in general, the more shots you take, the higher the odds of one that is awesome showing up. It’s simply odds.
Onto your actual question, your camera settings. You need the photo to be big enough for printing at 300dpi. Bigger is better, bigger is never really bad, so take the biggest shot you can take. This of course means bigger files, which means less capacity on your memory card, so you’ll need to be able to dump the card and take more shots quickly. There are also some ISO settings that you may be able to change. These vary depending on your actual lighting condition, but in general, the lower you can go, the better quality of still image you will get. But the camera needs to be exactly still, and so do you, when you get very low in ISO. So try around 400 and do some test shots.
Ultimately the exact settings don’t matter. What does matter is you getting the image you want. So if you can, bring a laptop so that you can check the image immediately when you take it, in order to tweak things to produce the best image you can.
If you want more info, you don’t need to tell us your exact idea, although in reality no one is going to take your idea no matter how cool it might be, ideas are a dime a dozen. It’s the final product that they’ll rip off. The more details you can give us, the better advice we can give you back :)