Redirect all .jpg 404 to gallery page?

Maybe a .htaccess rule would do the job?

Checkout this post on StackOverflow for a possible way to do it:
https://stackoverflow.com/questions/18502393/htaccess-to-redirect-jpg-to-a-webpage

For a more basic understanding of .htaccess see this guide: https://code.tutsplus.com/tutorials/the-ultimate-guide-to-htaccess-files–net-4757