I did something similar in December. I have a 30ft by 6ft wide concrete cold storage in my basement. I framed in a wall with 2x2 box tubing 1/8" wall thickness. For now I'm using a steel exterior door with deadbolt. A vault door will be added when budget allows.
I have a gun storage wall on one side and a workbench for projects and reloading on the other. I also plan to build some shelves for ammo box storage
The panels and hooks are Gridwall intended for retail display. It is nice and heavy duty. The wire is 1/4" diameter in 3" grids. I found it on KSL. There are tons of accessories you can get for the grid system.
I love what you did here, just wondering what you would do to insulate around the door for fire protection/heat, does it matter in a room with 3 concrete walls, ect. I have a similar space that may make sense to do this.
I figured that fire/heat damage would be rare since the cold storage walls and ceiling are all concrete. I did insulate the exterior wall (behind my gun racking) just to help keep the room at a reasonable temperature. I have a space heater set to 60* and a dehumidifier holding 25% humidity.