Although it sounds counterintuitive, many times darker colors work beautifully in smaller spaces. Maybe it's because they don't overwhelm and fatigue the eye as they would in a bigger area. Many years ago, I saw a beautiful Victorian style small bath. It had walnut cabinetry and wainscoting, floral stripe wallpaper in shades of burgundy, hunter, navy, and gold, the floor was glossy black tile, and the lighting was sconces on either side of a large beveled oval mirror. It was gorgeous! So if you want to experiment with chocolate, or cinnamon, or a busy floral wallpaper, go for it. Have fun!

blue

I have that same stupid tile in my shower! Not attractive but solid as a rock. Try using a curved shower rod to hide it. As for color schemes, find a nice shower curtain that you like and pull a wall color from that. Mud-toned blue, green or lavender would work. FWIW, light colors do tend to wash out in low light rooms so a mid tone might work better. And get some nice coordinating microfiber bath mats to hide the floor.

Kilz (I think) makes a primer called Upshot to prime ceilings. It’s an aerosol that sprays straight up. HD has it. You’ll want to use that to prime the ceiling before painting it with any brand of ceiling paint. The ones that start white and turn punk are easier to use so you don’t miss a spot.

How handy are you and your husband? That floor could be covered with a nice LVT or stone-look vinyl tile in a couple hours.