I used google's image search to find these crazy quilts pictures.
If you find a quilt similar to the variations of block sizes that you want, you can sketch it out on graph paper to help with the size of your blocks and how many you will need.
To figure out how large you want the quilt to be, maybe measure the bed you want it to fit? Not all mattresses are the same depth.
http://www.google.com/images?um=1&hl...=&oq=&gs_rfai=