Handy feature to display items.

/itf toggle visibility Allows you to toggle the visibility of item frames off and on. A message will pop up in chat saying if you have turned it on or off.

/itf toggle glow (color) Allows you to toggle a glow on the itemframe on or off.

https://www.spigotmc.org/resources/invisibleitemframes-better-item-frames.85085/