48 hours after 20% TCA peel. Is this normal? (Photo)

Thank you for your question. Darkening of the skin and a crust like scabbing is to be expected and will most likely slough off in patches. The application does look a little uneven but should all even out in time. Folow post instructions and follow up with the office that performed your treatment. If you are still concerned then consult with a Board Certified Plastic Surgeons office for further treatment. 

Typically, skin turns brownish and starts peeling within several days after a TCA peel.  Areas of high activity and lots of movement (around the mouth, for example) will usually peel before areas that don't move as much.  Your photos suggest peeling in progress at the cheeks.  I think your best bet is to follow your doctor's instructions the the letter, and keep a close follow-up with him/ her.  Good after-care, sun-avoidance, and possibly lightening creams are a key part of peeling aftercare.  Best of luck to you.