If you put the shower where the tub is you will need to remove or replace the wood window. I would look more into a wet room that doesn't need a shower door to open the space.

Lots of photo ideas in the search area.

I am looking to do the same thing. I am thinking a spa shower with the Kohler Bypass Shower Doors. Looks a lot like the frameless shower doors but at a third of the cost. Check this website for more information from someone who had them installed: http://ths.gardenweb.com/forums/load/bath/msg0808415130178.html?9
Also, for the spa shower look I was looking at the bar with the large shower head and handheld shower head. Kind of looks like a vertical grab bar with two shower heads. You can pay hundreds or even thousands for some of these. But for my budget, I am looking at the ones Lowe's has that run around $80. I like the culture marble walls for the shower. You cannot beat them for ease of cleaning. Tile for shower floor and wall accents. Also, I want a large rectangle cubbie in the shower for shampoos, etc. and a grab bar. Have not yet figured out if a teak bench might be good too.
You would need to replace the window and could use those glass blocks so light still comes in if you like the look. Where the shower is to be replaced with cabinets for linens, I am looking at the bottom portion to have those pull out trays that hold dirty clothes hampers. I don't have room anywhere else for them in my bathroom. Just open shelves for the top portion of the linen cabinet I think.