How do I make this go with my beachy bathroom?

Roll towels up an place them in it

Maybe put some Jars in the holes with sea glass, sand or shells in them. You can also add a flamless flickering timer tea light candle in the glass.

Hot glue shells over the scrolled areas.

It looks like this was designed for two bottles. You could buy or make aqua toned sugar scrubs and funnel them into clear bottles, or look for aqua bottles of lotion or soaps. OR

Put clear plastic in the bottom and use it for makeup/perfume bottles, brushes, curling iron, toothpaste tube, etc. It’s a pretty container.

You could hot glue a large shell onto it right at the top of the scroll. That would add to the beachy theme.