I'd be interested in seeing a build log if you have photos and care to post one.
Sure, I can do that. I'll throw it in the Back Porch after I get back from the wedding. In the meantime, you can click on the picture to see the pics I took while building it. It's brief, but it should give you an idea of the process.
Is the frame easily replaced in case it doesn't fit into somebody's decor?
"Easily" is a relative term.
The frame is a "backless frame" from Hobby Lobby. While it's easy to get a frame that matches your decor, you'd have to flip the mirror over and undo the dozen screws that are holding the box onto the frame. Best case scenario: A dozen wood screws and it will come right out and you can replace it. You'll have to drill new holes in the frame, but that's about it.
At a minimum, if it checks in you'll have its IP address. Anything beyond that is up to you. If the home router supports UPnP, a daemon on the Pi could automatically open ports for VNC or SSH. I believe most routers ship with this enabled out of the box.
You could have it setup a secure tunnel as a fallback in the event that UPnP is not available. As long as you have a domain registered on the public internet (or a subdomain on a dynamic DNS service), you should have no problems when the setup is outbound from their network.
Hmm. The dynamic DNS I already have. And I like the idea of the Pi us UPnP to open up a port and connect to my house, for no other reason than to let me know it's there and I can get into it if I need to. Let me do some research and see if I can figure this part out myself. I may beg for more assistance later.