Many years ago, I visited a friend who has a rather impressive black powder gun collection. In his "gun room" was all his re-enacting gear and some mostly non-shooting "wall-hangers."
At one end of the room, there was a gun rack on the wall with a Daisy BB gun and a fishing rod on it. Just below those two, was a shelf, with a pair of drawers on the ends.
He opened those drawers, reached inside and unfastened a pair of door bolts. . .
And that whole section of paneling lifted right out of the wall!
This hidden-in-plain-sight door covered a two foot deep "closet" that went the full, 8 foot span of that wall. The "door" was a 4 foot wide piece of paneling with the gun rack mounted on it.
Had he not shown it to me, I never would have seen it. It was cheap and easy to build, and only took a little bit of space in an already small room. He kept all his "good" guns in there, including several Civil War originals.
Might just use that trick myself, one of these days.
mm