Post Blepharoplasty and fat transfer, Ice should be applied to decrease the bloodflow and resulting edema/swelling to the area. The difference between ice, that decreases blood flow to tissues and heat that increase blood flow to tissues would depend on whether you are trying to eliminate swelling or not. Clearly after Eyelid Surgery, it's beneficial to decrease swelling and hence ice therapy is indicated.
The plastic and cosmetic surgeon or occuloplastic surgeon that does your eyelid surgery will give you specific post eyelid surgery, fat transfer instructions. FYI, IMHO fat transfer is not as reliable as office the shelf fillers like Perlane and Radiesse or Cheek and Chin Implants. Just food for thought.