There is a problem of rendering with hugo pictures shortcodes in blogdown. You need to frame the doble quotes of the picture source with single quotes.
blogdown::shortcode("figure", src = '"/img/blogdown-tutorial/four-pane-view-after-installation.png"', alt = "Some alt text")
With this workaorund pictured called via Hugo shortcodes should now show up:
YEP! It worked!
Image is shown but the alt text is also shown as normal text.
![my alt text](/img/blogdown-tutorial/four-pane-view-after-installation.png)