You should set ObjBrushStyle[] and ObjMemoCharsBrushStyle[] property.
For example:
ImageEnVect1.ObjBrushStyle[-1] := bsSolid;
ImageEnVect1.ObjMemoCharsBrushStyle[-1] := bsSolid;
ImageEnVect1.ObjBrushColor[-1] := clYellow;
ImageEnVect1.ObjFontName[-1] := 'Arial';
ImageEnVect1.ObjFontHeight[-1] := 18;
ImageEnVect1.ObjText[-1] := 'Hello World!';
Imageenvect1.ObjKind[-1] := iekMEMO;
ImageEnVect1.AddNewObject(iekMEMO, Rect(0,0,200,80), clBlack);