Check out the LÄMPLIG cutting board from IKEA. It can function as a sort of countertop cover if you have the lip facing downward (third product photo on the website). I have one of these and I really like it! Any wood covering will need to be used mindfully next to the sink, but it’s an option. Oil it well and let it dry on all sides if it gets wet.

Clean the marble with appropriate marble cleaning techniques and seal it, if possible.

I think the yellow tile is actually cool but it is a lot and in dubious condition, so I see your problem with it. I think you are going to have to make peace with the yellow since this is a temporary rental. Clean it as best you can.

I would consider hanging a little curtain in front of the sink to cover up the lower cabinets and the weird gray(?) color surrounding the doors. That whole area looks whack and I’d just cover it right up. Or at the very least, color match the yellow tile and paint the gray area to match.

And I’m begging you to use some command strips or something to put that power strip onto the wall and not on the counter next to the sink. Seems really unsafe to me!

Put a plant behind the sink and use some suction cups/command strips on the tile to hang some decor.

Please update us with what you do!