Display Unique Image Based on State?

I’m not sure if it’s possible to use a shortcode within the img src-attribute but you can try.

You can use the “Show/Hide-Text shortcode” and list all 50 images.
https://github.com/yellowtree/geoip-detect/wiki/API:-Shortcodes#show-or-hide-content-depending-on-the-location

Or use the flag shortcode:
https://github.com/yellowtree/geoip-detect/wiki/API:-Shortcodes#add-a-flag-of-the-visitors-country
and write the filenames of the states as CSS yourself instead of installing the flags plugin.

Or write some PHP code.

Beware to treat the special cases (what if the visitor is coming from outside of the US, or only the country USA is known but the state is not known?) …