If you're making a case before a BoD who are not tech-savvy, then the last thing I would worry about is a diagram of how the backbones look or operate. The BoD doesn't care, so save yourself the embarrassment.
Focus on costs and benefits instead. What is the cost of each: purchase, implementation, support, planned upgrades, etc. How stable are the vendors? What are the benefits of each option: improved network performance, lower operating costs, etc.
Don't tell them things like "xyzMbps" either. Tell them how much faster e-mail will be, how much less time their secretaries will spend waiting for files to open and close, or how much longer the preferred solution will be viable (i.e. how long before the next expensive upgrade).
Work it from this angle. If they ask tech questions, have the material ready, but don't be tempted into jargon. Watch out for glazed-over eyes!
Although some graphics describing the basic nature of each alternative would be useful, the best visuals you can give them will be charts and graphs of cash flows.
Good luck!