I'm trying to make a photo of a family and have it in a GUI in a Portrait, but one of the family members is a player. I can't find an efficient way of getting the player's avatar and having it with the family members, I've already thought of making the scene inside the game and using a camera to picture, but that isn't that practical.
iNot_Here is absolutely right. You could use GetUserThumbnailAsync. If you're thinking about how to put the image in the family portrait, assuming as you said you use a surface GUI, you can put the family portrait with a blank spot for the user thumbnail in an ImageLabel and put the user thumbnail in an ImageLabel above the portret and position it on the blank spot.
Edit: You can use ZIndex to position ImageLabels on top of eachother.