The biggest change I would make would be to swap the microwave hood for a proper range hood that vents to the outside of the house. this will make your kitchen and your home function better.

No one is going to be looking for/at moulding in a kitchen like this. It’s not that kind of space, but if you really want it you should consider copying the profile of the window trim.

As far as tile goes, you want a glaze color that works well with your cabinet color and your counter, so look at the counter veining - is that grey or white? Whatever it is, consider a tile that is a neutral or slightly warm version of that color. Same with the paint color for the wall. It should harmonize with the tile and existing finishes. It can be the same color, or a shade or two lighter or darker.

Good luck!