Hi, thanks for the question!
The little red flower designs on the forehead – that you often see on Hanfu wearers and in Chinese media & arts – are traditional Chinese accessories called Huadian/花钿, which came into vogue during the Tang dynasty. Please check out this post that I made on the history of Huadian.
Since they first appeared, Huadian have been an enduring symbol of beauty in Chinese culture.
Huadian come in many colors and shapes, in addition to red flowers/petals.
For more references, please check out my Huadian tag!
Hope this helps!
Ziseviolet 