Thanks, I made two 3D models (decorations) and upon interacting with a terminal I scripted it so that the 'lever_up' model got replaced by the 'lever_down' model. The only problem was that for some reason the 'entity delete' command did absolutely nothing and so I had to resort to 'entity move' in order to shift the 'lever_up' model into a wall so that it would disappear; not sure if it's a bug or I did something wrong, but the command is pretty straightforwards. Then I used 'entity spawnat' to get the new lever model appear where the previous one was.

I will try changing the textures via FSM once I've studied that well enough. Thanks for the help!

(EDIT: I understand it is possible to attach a script directly to the decoration, but still learning to do that)