An architectural visualization artist can work with several types of projects, even with fields that are not directly related with architectural projects. In my case, I already did some 3d modeling for projects related to Game Design and documentaries. In that case, you should practice the creation of antique architecture and do a lot of research. If you never had the opportunity to create antique architecture like the one from medieval times, here is a nice opportunity. I just found out a great set of three tutorials with almost 3 hours of video, showing how to model medieval architecture with Blender.
Here are the videos for the tutorial, which were produced by blenderpedia.
Um tutorial desse ajuda e ajuda MUITO quem tá iniciando, parabéns!