Also, what's an ideal size for a walk-in shower?

Right now we have a 3x4' shower, and it's adequate. In our new house, however, I want to add two things -- and adding means more space: 1) A seat -- this is to be our retirement house, and I know that my 99-year old grandmother has a shower stool in her shower. 2) Shelves for storing shampoo and soap. I currently have a Walmart-type pole-with-three shelves in my shower, and I don't particularly like it.

My husband wants a shower large enough that we don't have to have a door, but I'm fearful that such a shower would feel cold -- you know what I mean: The steam would escape. I do not like cold.

Any thoughts would be appreciated.

We do have a walk-in, door-less shower with a bench and I don't find it to be cold--& I am almost always cold anywhere else! Our shower is ~4'x7'. The entry is on the short end with the bench on the short end opposite the door. The shower head and handheld shower are placed on one of the long walls side by side. Our builder swore we would have 2 things happen--the shower would be cold and we would have water splash out onto the bathroom floor. He pushed us to install a heater over the shower, but we chose wait and see what we thought after we had actually tried it out. So far, neither of us are cold in the shower and we haven't had any issues with the water splashing out. We have an overhead rainshower, but we hardly ever use it. Here's a pic of our shower:

If you're thinking about planning for the possibility of needing a fully handicapped accessible shower you will need to plan for at least a shower thats 5'x5' to allow for a wheelchair to turn around in. This is what my parents have for just that purpose--their shower is 5'x6' with a 3.5' entry on the 5' side. I've used their shower before and it doesn't get cold either.

I will say, our seat could have been deeper--its only 12" deep. 16"-18" would have been more ideal. Another thought is to not do a built in seat, but have a removable stool/seat/bench--plenty of threads on GW on the pros & cons of each seat option.

As far as storage, the answer is niches built in to the shower wall. They are built-in so they don't protrude into the showering space and offer a myriad of options as far as how to set them up (i.e. shelves or no shelves, tall & skinny, short & wide, double decker or single decker, etc). If you look close in the shower pic, you can just make out the little ledge where our niche is and a sliver of an orange shampoo bottle just in front of the 1st shower head and shower controls.

Hope this helps!