Black Angel is a 1980 short film that was shown before the theatrical release of The Empire Strikes Back in certain locales. It was the directorial debut of Star Wars art director Roger Christian. The film negative was thought to be lost until it was rediscovered in December 2011. In June 2015, it was announced that Christian was working on a feature film adaptation of Black Angel, which would be part-funded by a campaign on crowd-funding site, Indiegogo.
Thanks Kam for putting me onto this.