1st Step... using a photo (that match your mental image of the drawing as much as possible) as base reference. Redraw it in your own style adding or removing any elements u want.

Using photos as reference also helps you understanding light/shadow behavior in clothing, skin, surfaces, giving a more realistic look to your drawings. War footage helped me a lot understanding how boddies usualy behave in a pile, scattered, amounted, twisted, so i could create a totally original pile o boddies with some acceptable level of realism. Quite stressing if u ask me, but the process worths the wile. 

It was looking a little empty, so we had to kill more people...

Felling lonely? Yay, bringing him a new buddy to make him company. Body count is growing bigger!!!!

Adding some Huey photos to the scenario, when redrawing the use of different details (colors, armament, passengers, fan position) on each one will distinguish them so it won't look like coppies. Omg, more boddies, need a bigger frame!

Nothing better to get a depth of field sensation than putting some blury barb wire in the picture... We can't have all those dead VCs running loose like that, can we? Safety first =)