VNC is an interesting beast on OS X. In Lion, OS X finally gained the possibility of having truly virtual sessions, meaning that they aren't displayed on the console. This is accomplished by enabling VNC, and logging in as a user that is not logged in at the console. That new user will have a private session to work in, and the console user will go uninterrupted.
If you're unsure of what I mean by "console", the console is the one and only session that a user directly attached to the computer via keyboard/mouse/monitor can use. That is commonly referred to as the "console" or "physical" session.
Note that on all previous versions of OS X, logging in as an allowed user could only put you on the console session, possibly colliding with a console user if they were actively working on the system at the same time.
On any other operating system, you can set up a private VNC session using almost any resolution you want, within a certain realm of feasibility. This is unfortunately yet to be the case on OS X. VNC still seems to hook into the physical capabilities of the system, perhaps this happens because the video card is used to render the desktop session even when you're using it remotely. Rendering the OS X animations is very intensive, so offloading them to the video card and freeing up general CPU time is an ideal situation for pretty much anybody.
So the answer? I don't believe you can. You can turn it down via the System Preferences like usual, but the highest resolution you'll get is that which is supported by your video card.
There's a subtle difference in the 2 technologies-- and kind of a misnomer.
Apple's remote screen sharing technology is based on VNC -- Virtual Network Computing. You'd think this would be a virtualized technology that would provide you with whatever screen resolution you wanted, right?
And Windows RDP -- Remote Desktop Protocol -- it would only give you what appeared on a remote desktop, right?
Wrong and wrong.
Apple's VNC-based Screen Sharing will show you what the user's preferences are set to. This is great for supporting a remote user -- you see exactly what they see, even if they have multiple monitors, you can pick and choose which one (or both) that you want to see.
And if there's someone already logged on to the system and you're connecting from another Mac? You're given the choice of whether you want to connect to their account's display, or use your own account's preferences. Multiple users simultaneously on one Mac, even with different screen resolutions.
So the trick is, set your account's preferences to what you want to see remotely; by default, that's going to be the native screen resolution your MacBook Pro supports. I think that once you've set those on your desktop, you're only given the option of scaling it on the Screen Sharing session if you're logged in with a user account not associated with a physical display (the Display preferences shows your remote session as an Unknown Display.)
But changing the resolution to something that's not reflected on the remote display? That's virtualized technology only supported by Remote Desktop.
Yes, confusion, caused by poor choices in names. Apple's use of Screen Sharing is probably the most appropriate name of them all.