With the constant growth in readily-available screen sizes and proliferation of large screens in public spaces, interaction designers are faced with the challenge of creating interfaces for large surfaces more often than ever. Contrary to mobile and desktop interfaces, design guidelines available to designers working with large screens are limited thus complicating the design process. In this paper, we report on interviews performed with interaction design practitioners with experience in creating large-screen interfaces. Through analyzing the interviews, we identify a set of challenges that designers see as important for improving the user experience of large-screen systems. We then contrast these challenges with findings from Human-Computer Interaction (HCI) literature to highlight practice-motivated research challenges. Our work aims at filling the gap between research and practice in large-screen interfaces and develops a practice-motivated horizon for future development.