I have more of a pool cabana. I don't have a picture of mine, but I built it 12'X24' with a pitched roof and a concrete floor. One end is 6'X12' which is the equipment room and bath/changing room. I did not put a shower in, as that would have required a water heater and much more electrical wiring for the service to the heater. The remaining 12'X18' is screened on three sides from about 2.5' from the floor to the eaves.
A few features: A drain in the floor next to the filter for getting rid of the water when I winterize. A screened vent right next to the pump (I'll be adding a small power vent high on the wall to circulate air through there to make it cooler). An outdoor faucet for adding water and an indoor faucet over the pump with an extension for rinsing bleach bottles. A ceiling fan in the screened area.
Size wise, the bathroom is a little tight on space (6'X8' roughly) , and the dining area could be shorter although it's fine as is. I'd move the dividing wall a foot if I was doing it again, but it's not worth moving it. Plenty of room for changing, but storing extra towels and suits would be easier with a little more room. Any bathroom at all is a luxury with kids, and having the changing area really keeps the dripping water out of the house. 12' width is about as narrow as you want to go to handle a standard patio dining set if you are interested in that. The 2.5' wall height was chosen to allow us to sit in chairs inside and still see all of the pool when the kids are swimming. The roof was pitched to give me a 9'X26' area for my solar panels, and the location was chosen to give me a south facing roof. I semi-planned for adding plexiglass panels to the screened openings if we want a place to sit out in the fall.
