Trying to figure out where to host high resolution images for customers for commissions. I would like to set it up so I can invite that user and ONLY that user to that particular image, but have the smaller res images hosted in the same place and possibly use it as another public gallery?

I'm open to suggestions.

The only ones I've heard of or seen other artists user are the following:

• imgur - large images, plus privacy settings I need. No NSFW images including classic nudity (not too worried about that last one, but if there's another option I'll take it).
• tinypic/photobucket - OMG SO MANY ADS. 1024x768 size cap. My images are currently 2048x2048 and will possibly be bigger for print options. I could be totally wrong and not understand their rules. I think it has private albums and you can link individual images in that private album? I'm not really sure.
• dropbox - Would rather this be the last option because of the size cap and the fact that I would have to create a separate account from my professional stuff.
• email - The last, last option. I would rather not do this because some commissioners are contacting me through places like weasyl and may not want to give me their email. Plus some emails have caps for size.