A raised shower always looks like a bandaid...I suggest you do it right and crack some concrete, put the trap below the floor then build a traditionally built shower. Resale will be better. If the room is quite large, you could build a raised platform so there wouldn't be as big a step up or out of the thing, but think of this...your feet will be wet, and that's actually larger than a recommended step...not the safest situation.
Check out www.johnbridge.com for help on tiling a shower. Personally, I found Kerdi from www.schluter.com works really well and solves some problems many people don't realize they have. Not that a conventionally built shower doesn't work, it does, but this is the next generation.