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This is a technique used in user experience. A great article called The Illusion of Time (The Illusion of Time) explains very well how human perception of time can be "dribbled" using simple features like an animated gif, see the Facebook example below.
Building this resource depends on which framework or library you’re using in your project.
The article Facebook content placeholder (Deconstruction of the Facebook content placeholder) demonstrates how this technique is done deconstructing the same used by Facebook.
legal +1 this I did not know ...
– novic