Very nice job. Isn't it always the way it goes? You make something to house a specific item or items, and then it fills up until you can't put any more in it. Leaving you to wish you had built a larger one. But you should enjoy the fact that you have a nice space for housing your thread. On the one I built, I lined the drawers with green felt. It helps to keep the thread from rolling around and makes less noise of rolling spools when opening and closing the drawers.
John