A custom css/html or gif/image file for the loading screen in R 'shiny'. It also can use the marquee to have custom text loading screen.

Create Interactive Graph (Network) Visualizations. 
  'shinyCyJS' can be used in 'Shiny' apps or viewed from 'Rstudio' Viewer.
  'shinyCyJS' includes API to build Graph model like node or edge with customized attributes for R. 
  'shinyCyJS' is built with 'cytoscape.js' and 'htmlwidgets' R package.

Create dashboards with 'Shiny'. This package provides
    a theme on top of 'Shiny', making it easy to create attractive dashboards.

Extend 'shinydashboard' with 'AdminLTE2' components. 
             'AdminLTE2' is a free 'Bootstrap 3' dashboard template available
             at <https://adminlte.io>. Customize boxes, add timelines and a lot more.

Provides three types of datetime pickers for usage in a
    'Shiny' UI. A datetime picker is an input field for selecting both a
    date and a time.

Provides a simple authentification mechanism for single 'shiny' applications.
    Authentification and password change functionality are performed calling user provided functions that typically access some database backend.
    Source code of main applications is protected until authentication is successful.

A 'Shiny' app can disconnect for a variety of reasons: an unrecoverable error occurred in
    the app, the server went down, the user lost internet connection, or any other reason
    that might cause the 'Shiny' app to lose connection to its server. With 'shinydisconnect', you can
    call disonnectMessage() anywhere in a Shiny app's UI to add a nice message when this happens. 
    Works locally (running Shiny apps within 'RStudio') and on Shiny servers (such as shinyapps.io,
    'RStudio Connect', 'Shiny Server Open Source', 'Shiny Server Pro'). See demo online at 
    <https://daattali.com/shiny/shinydisconnect-demo/>.

Add a download button to a 'shiny' plot or 'plotly' that appears when
  the plot is hovered. A tooltip, styled to resemble 'plotly' buttons, is displayed 
  on hover of the download button. The download button can be used to allow users
  to download the dataset used for a plot.