Is dimpling of skin after liposuction normal? I had 4 liters removed from my lower/upper abdomen and flanks. (photo)

The dimpling that you refer to in your skin is called "peau de orange".  Peau de orange means skin that appears like the dimpled texture seen on an orange peel.
Peau de orange is caused by cutaneous lymphatic edema.  A simple explanation to this fancy French terms is that your tissue is swollen, so much so that your lymphatics (the drainage system found in your abdominal wall as well as other places) is overloaded with fluid, and like a sponge, your skin has soaked up this fluid.  You may have some free fluid in your abdominal wall, but more than likely you had some free fluid and it got absorbed into the soft tissue of your abdomen.  
Each plastic surgeon has his or her own paradyme for treating this type of condition, so your best bet is to discuss this most interesting but not dangerous problem with your personal plastic surgeon.

You may have skin changes and swelling, which can last 3-6 months after your procedure. I recommend adding hyperbaric oxygen and lymphatic massage along with your compression to help decrease swelling. To improve your final results, I also recommend adding vanquish for further fat removal, exilis/venus legacy for skin tightening, cellutone/z wave to make the skin smooth, remove scar tissue, and improve the skin’s appearance. See an expert. Best, Dr. Emer

You skin changes are temporary and should subside in 3 to 6 months.   See your surgeon for assurance.  My Best,  Dr Commons