I'm going to also replace the white-on-white appliances with stainless
steel. What about a stainless steel backsplash throughout the entire
kitchen? I think stainless backsplash may look good to me and match the
new
appliances, but I don't want it to look bizarre to others if I sell later.

Stainless tends to show fingerprints. Stainless in commercial kitchens
works because you have staff that cleans it everyday. While I like the look
of stainless I don't like the cleaning effort it incurs in a residential
situation.

Pick something that cleans well and balances the overall look. As has been
mentioned, carrying the granite up onto the wall may be 'too much'.
Undercounter situations usually work better when lighter colors are used.
The available ambient light is better reflected back onto the working area.
Otherwise you're stuck with adding more undercounter lighting.

Frankly, unless it's likely to be extremely mess I've never had problems
with just using a decent semi-gloss paint. Why shell out all that extra
money to put up tile in a place that doesn't really need it? Why make the
room look 'overdone' with yet another color or pattern?

Also consider how that wall space might be used. If you want to hang
pictures or other things it'll be a lot of extra work if there's tile up
there instead of just paint on drywall. Fixing or covering holes in tiles
is nowhere near as simple.

I think tall granite backsplashes matching the counters might look busy or
overwhelming.