The fact of the matter is that it is impossible to make a room above a cold storage space equal in temperature to any other room in the house. However, there are ways to improve the situation, and that includes eliminating air drafts. The problem with older houses is that they are rarely sealed properly. The first thing to do is remove the quarter-round molding on the bedroom floor, and caulk the joint shut. If there are any other areas in the room that are likely to be the source of air drafts, caulk them too. Then caulk the joint where the garage wall and the floor above meet. These joints are rarely done properly, if at all. Immediately there will be a noticeable difference. Then I would suggest installing some fiberglass insulation on the garage ceiling and placing a drywall ceiling over that. Improving the insulation and eliminating the air drafts will not make the temperature in the room equal with other rooms in the house, but there will be an improvement.