Looks like a good start - enjoy the process & journey! I agree with what Mark & Joe have said. However, to better answer your questions I'll need to ask a few:
What does the space you have in the bonus room look like (i.e., dimensions & shape)? Are you committed to a rectangular table-top layout, or would an around-the-walls layout be an option? That might not only give you longer loops but open up possibilities for more &/or longer sidings, yards, etc.
What are your goals for the layout? Do you just want to loop-run a few trains at a time? Does the prospect of operations interest you? What type of equipment are you interested in running (e.g. traditional vs. scale)? Does the layout need to be "kid-friendly," or will it be more centered on adult needs/interests? Do you have any "must haves" and/or "don't wants?"
