List with flags for countries entries

For registration I would like to add a dropdown for the participants to choose their country, but in the list view in the frontend I would very much prefer to present flags of the countries only. How can I do that?

I tried it with “Germany::“, but that did work, that even get not stored. And with the shorter version “Germany::de.svg’ width=’20px’>” it got stored and the value “de.svg” was stored in the DB, but in the frontend still “Germany” is shown.

Can anybody help me? Best would be to show dropdown with list of country names, to store just two digits county code in the DB and show flag in the front end for visitors of the website.

Thx for any help!