Go to the john bridge forum. They give great help and advice on building showers (and all things tile-related). As far as the size of tile, it really depends on what you like and what feeling you are going for. I prefer tiled shower floors, but someone here (I think it was cat mom, but not sure), did her bathrooms with cast iron bases and raves about them.

I like the Kerdi system. Pretty foolproof and watertight.

I went through the same thing about 1.5 years ago redoing our basement bath. Needed a corner shower, hated all the fiberglass options (have a Kohler fiberglass corner shower in the 2nd floor main bath and have only been 'so-so' happy with it).

But, I didn't want to do a tiled shower because tile frankly isn't the ideal shower material. Grout is porous, meaning you need to do a full waterproof membrane beneath it, making the tile more or less cosmetic etc etc and grout just gets dirty.

I went with a solid white (no marbling) cultured marble corner shower.

The base is cast out of solid material - there is NO give in it - it is SOLID all the way through. The walls are panels of 1/2" thick solid material as well - NOT flimsy fiberglass.

The base sits in thinset like a giant tile on the floor. The walls adhere to plain old drywall with silicone caulking (100% silicone). The inside corner is sealed with silicone and I have a trim piece on it to cover the seam which is also held on with silicone. This thing ain't gonna leak ever.

Then we had custom glass cut for it. We started with a shower curtain, but quickly decided the glass enclosure was worth it.

I'd strongly recommend looking at cultured marble as an option. Was the same price or less than a decent quality fiberglass kit and is way higher quality.

I don't have much in the way of pics but here are a couple.

Oh - and as a compromise in-between sort of thing, you could go with a cast shower base and tile the walls. This way you have no worries about a waterproof floor and don't have the hassle of all the slope etc. to sort out.

For waterproofing a shower I'd recommend a Kerdi setup.

Even better than the Kerdi try using Laticrete's Hydroban. It's easier than Kerdi (in that it's a roll on application) and there are no seams to build up overlaps in corners. I'll still use kerdi for Steam showers, but for any conventional showers, all my showers are now waterproofed with the Hydroban.

I'm the same as Bill. Kerdi for steamers, Hydroban for non-steamers.

I'll start you off in the direction of a cast iron receptor for your shower pan. If they are not in your budget, come back and we'll move on to the other options.

With any base, your walls will be a piece of cake. Cement board over the studs, then the cement board covered with Hydroban. Then tile. Tile size is up to you, but it can depend on the how flat you get the wall. The flatter your walls, the larger tile you can use.

But let's solve Step One, the pan. Do you like CI? At $500-$800, are they in your budget? Don't forget that it's ready to go. Set it and forget it. Or do you prefer an acrylic/plastic pan?