The idea of making a texture for "sides" of a structure is not how it is done - you need to model the separate parts of the building. You assign material names to elements in the Archicad model.
Certainly the export file will take any texture image found in the assigned Archicad material over to Artlantis, but you will probably use a better material found in the Artlantis Catalog, or by applying material collections in Artlantis postcards.
It is fairly easy to make a reference file to automatically substitute the better Artlantis materials for named Archicad materials.
Dwight Atkinson