Does the NAS you are proposing to buy able to operate as a web or ftp server?
Does your router allow you to redirect inbound requests on specific ports to specified hosts on your lan?
Does your ISP allocate a fixed IP address to you, and does it give you an entry in their DNS?
In my case, the answer to all of the above is yes, but I still wouldn't use the NAS to share content. I'd put a web server on my network, probably running Linux and Apache (and I am a Windows person before anybody kicks off on that one) and use that to serve content.
You also need to consider what sort of broadband connection you have, since your download speed is probably much more than your upload speed. Maybe not much of a problem if you use fibre, but could be painfull for your clients if you still have copper.
If the answer to the above is no or don't know, or if you have no idea what I am ranting on about, use one of the many photo sharing services or rent web space.
You ask if it is good? Maybe. But only if all your current infrastructure supports it. Mine does and I still wouldn't do it, and if it didn't, I wouldn't spend time and money making it support it.
Nothing wrong with getting a NAS, though, for picture/music sharing on your local lan.