Supplementary materials can be anything that you created during the course of your research (data, code) or as part of dissemination (presentation slides, conference posters, graphical or video abstracts). You can even create something specifically to place in a repository (for example, creating a poster or infographic even if you are not presenting it at a conference.) Placing these materials in an open repository can drive people to your work by making them searchable via Google, appeal to busy people with brief summaries of your work or major points of interest, and provide digital object identifiers (DOIs) that will help you track usage.
The list of repositories on the Research Impact guide will help you to find a suitable place for your materials.
Graphical abstracts are "used to visually and concisely summarise your manuscript and its main message." (See Graphical Abstracts: How to Master the Latest Trend in Publishing) Some journals are now asking for these when they publish your manuscript and they will have their own style guidelines. Infographics can look similar but need not refer to specific paper.
The library has a data visualization specialist who can help you create visualizations and infographics.
Video abstracts have a similar purpose to graphical abstracts but require a bit more work. We Share Science is a sort of clearinghouse for video abstracts and has links to tutorials on how to create them. At OSU, the Digital Union in 063 Denney Hall has a one-button video studio that your can use.
DOIs and Tracking Usage
Not every repository creates a DOI when you deposit material but they are very useful for tracking online mention of your work. Altmetric has a free browser bookmarklet that will display online mentions for an item that displays a DOI. In addition, some sites will display statistics on downloads or views, etc.
This is an example of an infographic in the Humanities Commons repository showing the DOI and report of downloads and, next to it, information from the Altmetric bookmarklet.