Contact paper.

Can you post a photo?

I despise mortar set tile...Look into some of the new tile paints. Many house flippers swear by it. You can paint a field color and add a border, if you can paint it you can create it. Certainly a lot cheaper than a new wall.

Peg board or cork board won't offer you a very cleanable surface. This being near water I would seek a different alternative.

I agree with Eagle. Try painting the tile. Does not have to be tile paint as there are not many color options available. Can be done with latex and chalk paint, a stencil, and several coats of polyurethane or polycrylic.

Klenk makes tile paint not sure if it works on glass tile. Why does this need covering , what is the rest of the backsplash? Maybe some pics.