My advice is to buy a helmet with the NVG and Rails already mounted so you don't fuck up the alignment trying to do it yourself.
As far as accessories go: If it doesn't do something, don't weigh your head down with it.
^This
If your going for an impression (SEAL, USMC, Army, ect.), do research on what they wear and buy your gear accordingly.
(I'm just going to use a SEAL or SF impression for my examples)
In most of the pictures I see of SF in the field, they aren't wearing the carbon Fast Helmet, they are rocking the Ballistic version (No holes in the top. The real one offers more protection)
http://www.ebay.com/itm/181056716736If you are mounting NODs on there, make sure to buy a sturdy ass mount. I've seen multiple replica mounts break or fail in the field causing damage to the NODs (even though they are fake and don't work in the first place.) I'd go with a milsurp Norotos Rhino mount over a replica. They cheaper and more available than the Evike ones anyways.
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=mount+rhino+nvg&rt=nc&LH_BIN=1I don't think I've ever seen tan PVS-14s.
http://www.evike.com/product_info.php?products_id=32869Or you could get some kind of functionality out of them.
http://www.evike.com/product_info.php?products_id=38540This part isn't very useful in most airsoft games, but it is accurate since many parts of our military uses strobes on their helmets to IFF. G&P also makes a bb holder that looks like a strobe, but I can't seem to find one. This will also serve as a counter weight, when placed on the back of the helmet, and will help balance the NODs.
http://www.ebay.com/itm/MILITARY-DISTRESS-MARKER-LIGHT-FRS-MS-2000M-WHITE-BLUE-IR-STROBE-/150984128695?pt=LH_DefaultDomain_0&hash=item23275af8b7All that's left are patches and a head lamp and your are aesthetically set to go for milsim. Most of this in no wear near necessary for airsoft, but it looks cool, and that is the important part.
