Use pgf/tikz to draw ornaments — these are the pgf versions of the pst-vectorian package. See the documentation at the package homepage for more options.
The output of this graph is used as Figure 1 of the paper: Wangyan Li, Zidong Wang, Guoliang Wei, Lifeng Ma, Jun Hu, and Derui Ding, “A Survey on Multisensor Fusion and Consensus Filtering for Sensor Networks,” Discrete Dynamics in Nature and Society, vol. 2015, Article ID 683701, 12 pages, 2015. doi:10.1155/2015/683701.
It's based on http://www.texample.net/tikz/examples/hierarchical-diagram/.
Relevant link: http://tex.stackexchange.com/questions/226461/how-to-draw-hierarchical-graph-like-this-one.
Some quick examples of the tikzducks package! The latest version, which has an option for an Overleaf tikz, can be obtained from Sam Carter's Github repository.
This Blackboard beamer theme and template was created by Kazuki Maeda <kmaeda@users.sourceforge.jp> for Japanese presentations, but can be used for English (or other European languages) presentations as well. It has been modified to work with XeLaTeX.
p/s: The blackboard background was drawn with TikZ; the code is also included in the template.