Hey man! I see you have been hard at work!
Regarding costumes, I really like 5! Maybe its because it is way different from the rest, but I get that feeling of royalty coming from it, like bigger and strong silhouette, the fact that water itself wraps around her to give her the dress she needs gives out a powerful vibe, fitting for a Queen!
But I also like scaled bodysuit on 3, very alluring!
Regarding heads, I think 2 is the best, cause its more simplistic, and not as noisy in terms of design regarding dragon's jaw, just a few big teeth, instead of large portion of them, that just becomes distracting on all other options.
But about dragon heads on her, my favorite is 4, and i cant explain why
Good stuff mate! Keep up the good work! (and I updated my thread as well )