Probably not a bug. The game was developed for a few years before I was able to start commissioning art, so many scenes do not have art and just show a black screen instead. There are several scenes with art in most areas (like the first dungeon for example), but you may have missed them. You can use the scene reviewer in Elmgar to view any scenes with artwork you may have missed from the first dungeon after clearing it. (The scene reviewer is only for scenes with art.) If the scenes in the reviewer aren't showing art then there may be a bug going on.