Do you want to do a total gut job? Or just a refresh?
This is such a broad subject. You can paint, change the fixtures, if a builder grade mirror - frame it, new rugs and towels, add shelves, and so much more.
I made over my tiny half bath, maybe this will give you some ideas: https://thehoneycombhome.com/floor-stickers-in-the-bathroom/
I took my glass shower doors down and put up a shower curtain. Got towels, throw rug and stencils to match. Stenciled a similar pattern that is in the shower curtain onto a swinging garbage can and first aid box. Also used the colors in the shower curtain for colors used else where in the bathroom. Nice thing about a shower curtain is that I can change the curtain and look of the room and color theme anytime I want to.
But by redo do you mean give it an inexpensive face lift or tear everything out and put new stuff in?