Travertine is very porous. I don't think you'd want it where things splash & splatter.

Is that also porous?

It's very pretty but from what I'm reading, it stains. Is there anything that is not porous? What about porcelain?

Porcelain, glass (or even metal) are best for a non-porous material.

This is crema marfil. Just make sure it isn't too pink with your counter.

If you seal it properly it should be fine.

Your counters have lots of yellow in them so be aware. The tile backsplash is one of the very few I've ever seen that looks good with an accent tile running through it.

St. Cecilia is too yellow for travertine which has a brown undertone. Crema Marfil is a good choice and there ar lots of profiles. You might also try a simple soft yellow ceramic that had some handmade qualities . .your traditional cabinets and dark hardware would be great with a sort of artisan approach on the splash.