Quote from ZackerPersonally I prefer concept drawings to be as detailed as possible. I like if they contain a wealth of detail so that I as a level designer can just pick out all the good ideas I like until I reach the level of detail the engine can handle.A concept sketch is supposed to give the overall picture and to give the level designers ideas of how to build their level. It does not matter how detailed the concept sketch is as the level design result does not have to match it exactly - it is concept after all.
Exactly. The purpose of the general concept art is to establish aesthetics and themes. Now, if a mapper/modeler is given a modelsheet and concept and told "reproduce this", that's one thing. But mapping itself isn't just following directions, it is a creative process. Concept artists don't generally know how exactly to plan for good gameplay, or have a sense of what makes for good resource management.... just what looks good. A good level designer takes that information, combines it with his own knowledge base, and composites all of that into a fun, playable level while adhering to the overall themes of the game and the art.