public class IdFieldConversion : IPropertyConvention, IPropertyConventionAcceptance
    {
        public void Apply(IPropertyInstance instance)
        {
            instance.Column( string.Format("{0}ID", instance.EntityType.Name) );
        }

        public void Accept(IAcceptanceCriteria<IPropertyInspector> criteria)
        {
            criteria.Expect(inspector => inspector.Property.Name == "Id");
        }
    }

/// регистрирую так...
Fluently.Configure(config)
                .Database(
                    FluentNHibernate.Cfg.Db.MsSqlConfiguration.MsSql2008.ConnectionString(
                        ConnectionString.GetConnectionString()))
                .Mappings(m => 
                        m.AutoMappings.Add(
                                new AutoPersistenceModel()
                                    .AddMappingsFromAssemblyOf<FluentNhibernateLocalSessionFactoryObject>()
                                    .Conventions.Add<IdFieldConversion>()
....
                            )
                    )
                .BuildSessionFactory();