How do I update this bathroom?

There are curved heavy duty shower rods that can be shortened with end caps that can be screwed to the wall. The wonderful world of beige - been there done that. A nice soft color can be used to hide the wall connections for the wall panels. The counter top can be replaced or the tile painted along with the cabinets. A pretty curtain on the window can enhance the new shower curtain.

I would paint the walls light gray or white, and add a good mirror above the sink. Is the mirrored medicine cabinet for toddlers? The light looks bad for shaving and makeup. Can’t see the shower, but buy a curved rod for most baths or showers. Use a liner to stay inside the tub or shower, and the heavy curtain outside. Get two thick, washable shower rugs so you have one to use and one to wash. Use nice pretty towels to add color along with the shower curtain. The sink needs a taller faucet and nice handles to look more modern, but don’t give up your counter space. Best wishes ☺️

I love the look of white beadboard half way up the wall. A soft blue/gray or green/gray color, on top half of wall. A new shower curtain with a little color. You dont need a heavy shower curtain. Use a shower liner, with a cloth, not plastic, shower curtain.

I believe fiberglass can be painted using a good primer.

I would lighten the bathroom up with a sand color paint. Bead board at Home Depot comes in PVC and is great for the bathroom. No painting necessary and cleans up great. You can get a tension rod for the shower or a curved one. Get one with bright colors of you choice. Have fun with it. To paint the walls, use a good gripper primer.

I don't know if this stuff will work. I have successfully used window film on windows. Window glass is slick and so is fiberglass. Its not that expensive so if it doesn't work …….. Also it can be removed without damaging the fiberglass panels. Theyre not all white or lacey some have pattern and color.

https://www.google.com/search?q=window+film&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjeuLq936nfAhWI5YMKHTxgDPIQ_AUIDygC&biw=1366&bih=619

If it were my bath I would get rid of the existing medicine cabinet. It sticks out from the wall too far and its too low. Replace it with a framed niche that matches the new medicine cabinet in height. I would inset a new larger medicine cabinet in front of the sink that looks like a large framed mirror. You need a mirror in front of your sink. Use glass shelves in the niche Every day items would go on the glass shelves in decorative boxes, bottles and apothecary jars. That should clear off the counter while still making things easy to get to.

Replace your missing ceiling tile and then paint them all. Or just replace them all. Your bath is small and theyre not expensive. I would keep the existing shower rod and replace your curtain with a traditional shower curtain and use decorative hooks. That will cover the rod and add some softness.