One simple way to display a model on a wall is to use an horizontal surface to detect the level on which the artwork, or hanging element, will display. Following are some videos realized with iOS devices.
You can for instance stick a small box to the wall :
You can also use any temporary surface to set the model's position, such as a book :
If you prefer placing your 2D artwork on a table, or if you want to learn how to set a 2D image vertically as in this tutorial, check here.