As a person who works underwater quite a bit I have always been facinated by Hard Hat diving...never had a chance to do it but always wanted to.
Luckily for you I work at a museum where we have a Mark V Scuba Helmet that we have rigged up so visitors can try it on...and so I was able to take a couple of pictures.
Here is the Front:

Here is a shot from the side where you can see the air hose and telephone connections on the back of the helmet...the telephone is the capped one:

And here is the obligatory goofy picture of me in the helmet:

Sorry about that...

Also we have a wonderful US navy video that describes the techniques of dressing into one of these rigs...and man what a process! I poked around on Youtube and found some [pieces of this video...tons of info here!
I hope those are helpful for you. If you need shots of any other equipment let me know we have the complete outfit here...actually one that was never used so its in amazing condition.
Cheers,
Blue