I am a newbie and i have been agonizing over how to make a simple gallery for my R maps in Shiny. I simply want to upload pdfs/ pngs I have created into a layout like this :
The R Graph Catalogue (your second link) has its code available in its GitHub repo here:
Show Me Shiny is powered by wordpress (according to its footer).
There are a bunch of great Shiny tutorials over on the Shiny developer page (below):
FYI, I'm moving this into the Shiny category, since it's related to Shiny. However, I think you'll likely need to do a bit more work on your own before the scope of this question is answerable.