I made a Master Chief Helmet from Halo a couple of years back for a space girl shoot. I didn't really finish it to a high standard, just painted it up with all the facets still in place. Seemed to look OK to me, however I liked the Pepakura system so I decided to look around for a Predator Bio helmet design and I found this PEP file
You will need the Pepakura Designer software which can be used for free with limitations. You can get the software
I downloaded the PDO PEP files, then had to re-arrange it because I am using A4 card for mine and the PEP is set up for Letter. No big deal, just shuffle the bits around.
I did find a different PEP file set up for A4 AFTER I had finished this, so I may decide to build that as well later.