As has been mentioned, it is very difficult to give you an answer based upon a photograph. The one thing that I can say is that Lupus is known for having many different types of rashes as its symptoms. There is even a form of lupus that affects only the skin. The primary skin issues in Fibromyalgia are dry/itchy skin and skin pain (my pain feels almost like a burn; it is very sensitive (painful) to touch and sensitive to temperatures).
70 and 80 percent of all fibromyalgia sufferers have some sort of skin symptom. These symptoms can be annoying by themselves, but can also aggravate other typical fibromyalgia symptoms. Dry skin is the most common skin symptoms associated with fibromyalgia and many patients suffer with chronically dry and cracked skin in various areas of the body. Hands and fingers seem to be particularly affected and symptoms can become so severe that skin begins to peel and can become very painful.
Skin rashes can bee seen with Fibromyalgia and they may be the result of dry and itchy skin that is continually irritated. Some rashes may appear as raised bumps and can be scaly to the touch. A skin rash with FM may also be associated with mottled skin. Fibromyalgia patients can develop areas on the skin that change color or tone and then become irritated when exposed to the sun, causing a rash. These mottled areas of skin can occur anywhere on the body, but are most common on the inside of the arms and thighs.
For a better explanation of Lupus skin rashes, you can refer to the sticky "Lupus Symptoms" or put the term "Skin Rashes" in the search bar and read all of the threads about the condition.
So, basically, both conditions can have skin rashes. Your doctors will probably have to run tests in order to determine, definitively, which condition is causing yours. However, do remember what Steve said, the symptoms and treatments of both conditions are so similar, that it may not be very important to have that definitive answer, as long as the treatments are working. I wish you the very best, and good luck
Peace and Blessings