I actually made fake boards from the extruded foamboard (the blue or pink kind people make tombstones from) and painted them to look like wood. It was in historic quarters when we lived at Ft Riley and no one there had any problems as long as we took them down promptly after Halloween. Of course, they also had an official Ghost Tour that the historical society put on each year, so that tended to make them a little more Halloween friendly, perhaps. Everyone's housing office seems to be different. The velcro is a good idea as long as it isn't overly windy where you live. The added bonuses of using the foam are the light weight if you take them with you next time you PCS and the low cost if you decide to donate to a friend who's not moving yet.
Sometimes you can find a theme you like that goes along with the history of the post/area; possibly a Civil War Cemetary if that fits in with where you live, or for an Air Force base maybe go with a haunted hangar type theme. If I was near the West Point area I would do the Ghost of the 47th Division or Sleepy Hollow or Civil War ghosts or just ghosts of grads in general... A theme does seem to work well whether it's a small or a large yard; for my new larger yard I divide sections of it into smaller subthemes. The graveyard is the main focus, but I also have the Spider's Lair and bat cave on my long low porch and my garage area.
