Pretty much all the maps created by the guild are some form of Reference map, displaying a broad range of general information. In real life, the vast majority of maps created are highly specific Thematic maps which display one or more specific data sets, usually in order to fulfill some particular purpose (A map of the distribution of an invasive species in order to convince someone to take action to contain it.)

So, my suggestion for a challenge is to create a thematic map. It might be a map of Orc Population Density, A comparison of psionic background levels against instances of schizophrenia, or a map of magic levels, transportation systems, and local legal status of mages as part of the process for selecting the location for a new magic academy.