I often say to people that curcumin is the next fish oil. I say that because it has so many health benefits that everybody should take it. It will actually make any diet plan better because it helps with fat loss as well as decrease whole body inflammation. I highly recommend it.
Creatine is also fine. Even though it is technically a protein (actually a mix of several amino acids) it will not screw up the diet by boosting insulin release or affecting your overall caloric intake.
I find that while on a fat loss diet creatine can often helps psychologically: you don’t feel as flat while losing fat (muscle stay fuller) which helps mentally. Oftentimes people who want to be muscular freak out when they start to diet down and feel their muscles getting flatter (just a loss of intramuscular glycogen/water)… they think they are losing muscle mass and then they stop their diet. Creatine can help you avoid that pitfall.