My partner thought it would be realistic to use some domestic festivals or European festivals, and Wikipedia shows some major film festivals in Croatia:
But it does not mean they are the best choice we get, and I knew about Fantastic Zagreb Film Festival since I was about to attend it last year. It has a short film programme:
It is confusing to look at the website, it is not clearly said the requirement of submission films and it seems to be higher standard than indie film. On top of that, it is not saying will hold it again in 2016, even the website URL stays as http://2015.fantastic-zagreb.com.
Luckily, my partner found a really cool short film festival called 25 FPS Film and video festival (http://www.25fps.hr/en), even the name is more modern and creative!
As you can see, the button ‘Submissions 2016’ is clearly shown on the home page, and I checked it out:
Our film will fit in for sure, and it will be nice to have its logo on our postcards even without submitting: