I would probably go with a simple white subway tile.

Your color palette seems to be grey, white, (and blue) so those are good options for your tile. White will make the counter/backsplash area look more prominent, grey will make the backsplash disappear into the wall. So start by looking for a white that looks good with your cabinets and your counters, or a grey that looks good with your paint.

I would leave the backsplash painted. It looks good, and will work well. However, I dont see or feel beach or coastal in your kitchen. You need some color in there to give it all a beachy vibe. Now it feels like the kitchen of a city condo.

Actually, is that cabinet holding your microwave hood the right height over the range? If not, you want to correct that before you tile. Just double check the specifications and installation instructions for the hood.

You need a backsplash to protect your cabinets and sub floor. There are several advocates for paint as a backsplash. They don’t understand gravity or the destructive effects of water on laminated wood.

You have nice cabinets but I don't find the wall colour gives your kitchen a coastal feel. The space above the sink looks empty, perhaps install either white of wood shelves above.

I agree a white backsplash would be a good choice, different styles to choose from.

Will you have any island pendants? What colour hardware and faucet do you plan to install? As for the style/colour for stools and table, can you show us what style you already have in your condo?

Agree with Eam44 - the OTR MW appears to not be installed per the manufacturer's specifications.

If too high, not only is the normally barely effective venting now pretty much no longer effective at all, but unless you're all over 6'5" or even taller, that MW is not at a safe height.

Maybe it's an optical illusion and it's installed correctly -- check though.

Perhaps just an optical illusion...