Sealing it will change the color, but unless you're planning to protect it with clear glass, I'm not sure you have a lot of options. If you don't seal it, it will still change color over time, with areas closer to the stove exposed to atomized oils becoming darker than the surround. And it will stain. Seal it. You can also put sheet stainless behind the stove to protect that potentially messy area.

I'd go for clear glass.

Agree with clear glass - roughly the width of the hood, from cooktop to hood bottom, attached to the wall.

I like the clear glass idea, how would it be attached?

anyone else have ideas. How does one attach a glass panel without seeing the attachments? Is there such a thing as glass that wouldn't reflect light too much?

Like a mirror, so bottom rail or clips. A glass panel would sit on the 3" backsplash, maybe with a little track, and top clips would disappear behind your hood.

You need tempered glass. The cheapest glass sheets I found are from IKEA (like their glass tops or glass shelves)

http://blog.diynetwork.com/maderemade/2012/03/08/emily-winters-bathroom-renovation-day-14/

and

http://www.homedepot.com/p/Erias-Home-Designs-72-in-J-Mold-Mirror-Mount-208146/202300818

Thanks. I have someone installing our shower doors soon, so I'll ask them about a custom sized panel to fit our space.