Initially, we asked them to do things "realistically", but not looking too brand new. Eventually, we had a good set of models that we could use as a style reference. We had to redo some models that were not fitting the style and we still have a list of models to improve.

One thing that we learned early is that all models need to have a common scale, otherwise details like doors look bad when scaled differently on each model. We have established a metric system, each tile in game is 2x2 m, all railings are 1m tall, all doors are 2m, etc.

Now we have a doc with all our notes regarding style and rules that we share with new artists.