Hi there, welcome to the community. Hope you enjoy your stay. [excited]
That's pretty simple to create actually.
It's just a sillouette.
Open a photo with a group of people in it; similar to the example you posted.
Zoom into each person one-at-a-time, and using the Polygon Selection tool, trace a selection around them. Since it's for a sillouette, the trace doesn't have to be perfect.
When you have the first person traced with a selection, press Ctrl+J. That copies them to their own layer. Repeat this for each person you want to use from the photo.
Once you have your group a people extracted onto their own layers, turn off the layer of the original photo.
Fill the background of your document with whatever colour you want to use.
Switch your Foreground colour to black.
On each layer of the people you extracted, press ALT+SHIFT+Delete. That will fill each person's shape with black.
Once each person is filled with black, connect all of the people layers by clicking in the small square to the right of their 'eye' icons, on each layer. When all those layers are linked together, press Ctrl+E to merge them onto one layer.
Now simply lower the Opacity for that layer until the sillouette is the desired shade of the background colour.
Any questions, just ask. [honesty]
