Our house has a downstairs shower room in addition to the upstairs bathroom. We actually hardly use the bathroom (I hate baths, DH and DCs have them very occasionally) and prefer the shower cubicle downstairs and the fact it's a decent shower, so a heavily used room.
To get to it you go through a study. It is part of a side extension built by the previous owners, as with everything else here, it's a bit crap in terms of the layout. Shower room is probably bigger than it needs to be and study is fairly small but has an archway, a door, a boiler and a large window so very little wall space. All of these things are on different walls.
I had the idea to move the wall about 45 cm back into the shower room, which would take the wall up to the window in there and create a bigger study and move the door to the opposite side it is on so we have a corner of wall space. My theory is when the DCs are older, they may want space somewhere for another TV/games console and sofa. We currently have 1 and it's in the living room and it's a long, open living room/diner so don't have the option of a second TV/games console in there.
But, I've been on pintrest looking at storage options as I also wanted a cupboard built in the shower room for the dehumidifier and other storage for crap. There are some great ideas that we could do in a small room but I don't know how cramped we would make it if we make it smaller. A shower cubicle, toilet and sink would fit fine in a smaller room but we also dry our washing in there when we can't get it outside.
Would you just leave it as it is? My more basic idea is just move the door to the shower room so we still get the corner of wall space in the study, it would just be the same size room but a bit better in terms of what furniture we can get in there.
I've attached photos from when the house was for sale. The shower room looks the same, the study has different furniture in. The door would move to where the plant is.