Painting of Matches Malone hides something

[Aperson43110]

I was out exploring the demo of Fallen Aces Demo map and in the office/matches Malones office, I noticed that there is some sort of area behind the painting, A safe like area, small area. I was thinking that in order to get whatever in the safe I need to first of all lift the painting of matches malone himself. But I am been figuring out for the past hour and a half. I think the clue delia gives us to open the painting/safe is "Death Head" but I have no idea what that means and if it even does something.
Please help me. I am dying to know what is behind that painting. Please I am dying to know what is in the area behind the painting in Mr. Matches Malones office upstairs.

[Wolf Knight]

if you need help with a game or have questions about a game, it is best to post in that games forum

[76561198279175278]

The cabinet under the painting has an interactive button on the right side. I also combed the entire level before noticing this, I expected it to be more complicated.