Well, here's the latest on this project. I discovered that my people painting skills are not up to par, and that experience and comfort in Photoshop transport poorly to GIMP. Needless to say, I've altered my game plan a bit. I will no longer be hand painting all of my art assets for these two images.
As you can see in the images here, I've added some photo textures as well as photos of real people. Well, I'm not sure how I like having the real people in my images so they may get cut before the final version is done, but I'm certainly enjoying fiddling around with the photo textures.
The trick is getting the textures to pack just the right punch. You want them to be noticeable but not overpowering from the rest of the image. I play quite a bit around with the layer style and opacity to get the right look, not to mention the transform tools to get everything to size and in perspective. The channel selection of the shape of the helicopter is invaluable here, allowing me to quickly delete anything outside the shape of the helicopter. I have also made a channel selection of just the windshield, allowing my to delete that from within the helicopter selection.
I'm going to be adding some more textures and painting in some of my own details, and then it will be time to do some overall adjusting to each image to make it look just right. They're almost done now.