Well... hmhm... lets start.
Make a program that will have in center ,or anywhere else ,big window in wich you see soldier untextured in 3D. For example by holding right mouse button you rotate him, and so on. Then you import pictures (*.jpg, *.bmp ...) in the program and then you select, in special toolbar, some picture that you want to be on your unit. Than drag it to the surface of the soldier in a big window (Like in 3D max)
Then you move selected picture and set it while the picture is on the surface of unit. And then you add another one and so on... Just make is simpler than 3Dmax or Oxigen.