My first impression is that the rise on the stairs is a little high for a person scaled that size. In RL, they look like theyd be about 10 inches high (Im guessing youre using a 6' high man as your "ruler"), while the industry standard for safety purposes is more like 7 or 8, depending on where you live. Curiously enough, if you increased his size so the top of his head was more or less level with the top of the mezzanine and then scaled up the height of the bannisters on the mezz level, the scale of the entire place would probably snap together just fine. And Im really not sure about the railings. Just for myself, Id lean more towards the glass wall idea: it would give your space a cleaner, more "Euro" feel in the design, particularly with the nice curves in the upper-level balconies. But with the bannisters and railings on the mezz level, again, Id watch the scale: right now, they look about 4" thick, and thats huge for a railing. But feel free to disregard; this is all just the wanna-be architect in me talking.

Hmm... I see what you mean about the railing - I can squash 'em down a bit to make them more manageable to the eye. The lower (flat) part of the railing could be made translucent (about what glass would look like), which would keep them subdued, and would also help camoflage the back walls a bit for the renders (the back wall will prolly be flat with door/window textures + a bump map to make it look like a real wall w/ doors and windows, so that they can be changed or modified to suit the artist's wants without hosing up the rest of the structure.) Speaking of back walls, each back wall will probably be a seperate .obj file, as well as the elevator car, counters, benches, chandelier(s), etc. That way, the whole thing is more flexible. Same story with the roof (a vaulted arch which can be removed to make it an outdoor atrium...?) The rise on the stairs would be a bit more tricky at this stage, since they were the starting point for the rest of the room, and changing them would require modification of everything that touches them. With the right texture, I think I can minimize the appearance of height (something that gives the impression of an "overhang" when seen from the front, perhaps?)

I dont think you need to change the rise of the stairs, just change how you perceive the overall scale of the room. Youll still have a massive space, even if you scale up the human figure.