You have various options, as your asking I'm assuming you don't use a pattern, PIN or Password lock on your N7 or you do but your asking in case you let people view your N7 and want to hidden specifically those pictures.
So other than those security features you could create a .nomedia in the album, what this does is simply stop the pictures showing up in your Gallery application. Now this can still be bypassed by a file explorer in which you could view the pictures.
Alternatively you could disable the stock Gallery app and install a 3rd party Gallery app like Quickpic in which you can either hide folders or password protect hidden folders, that way none of your folders containing the pictures in question would show in the Gallery unless you opened the settings and chose to "show hidden folders".
Finally you could install an app like Hide it Pro from the Google Play store.
Hope that helps, now if I send you my email address..... jkn