11 months post 4000 grafts FUE, what can be done to thicken my hair? (Photos)

It can take 6 to 12 months after surgery to see results.  If you are concerned it is best to contact your doctor.  Your photos look confusing as you seem to look worse after surgery.  Please discuss with your doctor.

The area transplanted was quite large and will not create the desired density. Plus, some (many) of the grafts did not grow and thus giving the light coverage look. Doing 4000 grafts in one setting with curly hair is very challenging and if done poorly or rushed could lead to negative consequences. 
Was this procedure done in one day or two? Was it a sharp or semi sharp punch? Did the extractor physician have experience with curly hair?

A second procedure would give you more density, and though things would be better your scalp would probably still show in bright sunlight or when your hair is wet.  Scalp micropigmentation would be another good option to make your hair appear significantly thicker.

I would recommend waiting for at least another 6 months before you have another procedure done. At this point, it appears from your photos that the hair has 1 - yet to grow, or 2 - you had a lot of failed grafts that did not grow. Hopefully the hairs are still dormant and will grow start to grow soon. If not, you had significant graft failure from your procedure. At that point, you will need to consult with a reputable hair restoration physician to find a good solution for you.

What shows in your photos does not look like 4000 grafts that have grown in. I always tell patients that their recourse is to speak with their surgeon if they are every disappointed in their hair transplant results. Good surgeons care about patient results and their satisfaction and it is their surgeons that set the expectations that are needed. The discussion with your surgeon is not and should not be confrontational. It should be a cordial meeting where you can discuss what you are seeing on your head and what expectations you had going into the surgery. Sometime, the results fall short and if is the case, try to find out why that happened and if you both communicated properly on the expectation issue.