I haven't actually hooked up my "outdoor shower" yet but I kinda have plans to when other things are not more pressing. Anyway, I've set up an outdoor kitchen space and I got a couple food grade hoses to run from the house water supply out to a utility sink I set up so I don't have to run to the house for water for canning and such. (I'm lucky I'm on well water) What sort of roof surface are you going to be using for the rainwater collection? And how will you make sure you can wash that roof off before you collect that water to shower with (ya know, bird poo, road dust, pollen and all that might not be so great to wash with.) Don't get me wrong, I like using rain water but I'm not sure I want to bathe with the stuff that comes off my roof since I see what collects in my rain barrel. Anyway, so you want to look into rain water collection and ways to wash the roof before you start collecting the water and perhaps a way to filter the water a little too. Then you want a way to heat some of the water, for that you might want to study up on Solar Thermosiphon water heating, for that you will probably need a way to support the hot water tank above the solar heating tubing or panels and you will probably also need some sort of pressure pump to provide water pressure for the cool water system that will also keep the hot water tank topped up as you use the hot water from it as well. Ya still sure you don't want to hook into mains water for the outdoor shower? A camp shower hooked to the rain barrel is probably the easiest way. I think colman makes something that will even hook to a propane tank for the heating part of it and has a little pressure pump or something like that, not sure as I haven't really researched it myself lately. Good Luck, showering outdoors is so nice in this climate.

I don't have a suggestion of specific color, but if you have a SW or BM store nearby, you can get a sample card of all the different whites they have (there are dozens!). Sounds like you'd like a white that's tinted with yellow or gold. You can ask at those stores which whites are tinted to the creamy side. Then take the card home and see which color looks best against your house color.

You need to get a bunch of chips from all manufacturers, toss them on the floor and see what they look like. See the link below for the method. It's easy, and you end up with way better colors. Here is a link that might be useful: Picking Paint Colors

I would skip on the fireplace, it will only block the view and that is the only area of the house you can make an outdoor gathering area if anything I would make that porch area covered or a nice trellis over it.