Mixed Reality (MR) popularizes numerous situated applications where virtual content is spatially integrated into our physical environment. However, we only know little about what properties of an environment influence the way how people place digital content and perceive the resulting layout. We thus conducted a preliminary study (N = 8) examining how physical surfaces affect organizing virtual content like documents or charts, focusing on user perception and experience. We found, among others, that the situated layout of virtual content in its environment can be characterized by the level of spatial as well as semantic coupling. Consequently, we propose a two-dimensional design space to establish the vocabularies and detail their parameters for content organization. With our work, we aim to facilitate communication between designers or researchers, inform general MR interface design, and provide a first step towards future MR workspaces empowered by blending digital content and its real-world context.