I have tongue & groove pine walls - need suggestions for backsplash

you can poly the toung in groove, or fill in the grooves with a wood filler, and apply your chosen back splash.

I am assuming you are referring to a kitchen. Here is a site with 13 ideas to choose from: http://www.bynumdesign.com/blog/13-beautiful-backsplash-ideas/

I think a stone tile backsplash with varied colors and tones would be great. Not too country, a bit elegant. Maybe a bit lighter than these, but....

https://www.wayfair.com/home-improvement/pdp/abolos-ardesia-random-sized-slate-splitface-tile-in-sonora-abos1584.html

I would paint the pine wall with a semigloss paint and consider something decorative for behind the cooktop.

One newer ideas of interest to me is firebacks is to use that near the stove cooktop. Depending upon your lighting and decor sometimes a pop of black it’s really attractive in a room.

Consider looking at Houzz and Pinterest for ideas.

http://www.woodlanddirect.com/Fireplace-Accessories/Firebacks

Coloured Plexiglass.