Entities contain objects for storing graphics related information via their IAgPointEntity and IAgPolylineEntity interfaces. For example, the Label property is an AgLabelGraphics object for specifying the entity label in a display. These properties are null by default, which indicates that such data does not exist for that particular entity. When using the RT3 query capability, these properties are set automatically by the query objects in an RT3 client application. If you are not using queries - for example by using entities directly in the broker - you can set them manually yourself.
AgFileModel fileModel = new AgFileModel();
fileModel.Color = 0xFF00FF;
fileModel.FilePath = @"C:\Path\To\My\File.mdl";
fileModel.ScaleValue = 1.0;
fileModel.Show = true;
PointEntity.Model = fileModel as IAgModelGraphics;
STK 11.2.1 Programming Interface