Its pretty easy to take an exiting one that works for you and copy the folder then empty out the contents and drag folders from framework or other things into appropriate folders and it should work fine. I've done a few myself now. Not a complete theme, yet. But i'll soon get there
Try it out with a few easy things first say battery icon's or 3g or wifi, or better yet all the above, find what you like best since they all sit in the same folder its easy to setup the MM.