You can do this by adding an img tag in the navbarPage()'s title argument. It would look like this:
navbarPage(
title = div(
div(
id = "img-id",
img(src = "path/to/img.png")
),
"Superzip"
),
# Insert rest of ui code
)
Then in you can style the img-id div as follows (this would be what it would look like in styles.css script in that repo):
#img-id{
position: fixed;
right: 10px;
top: 5px;
}
You will probably have to play around with the top and right css values but that should give you what you are looking for.