The form of the plumage often don't follow the form of the skull, especially weird display structures are the opposite of form-true and this is not even the strongest example of how the skull of an bird can dissapear under feathers, when you look at this guy: [link]
you wouldn't guess that a skull like this lay under it [link]
It's very likely that nonavian dinosaurs, maybe even pterosaurs had similar misleading compositions of integument.
For this picture, again painted with Gouache, I searched for a small theropod with no intelligent, fast or big prey, because those structures would be hinder the hunt of such animals or would ruin it. it must be a food source which you can find everywhere so the animal can take long rests to preen and courtship.
My choise fell finally on the smallest known theropod from North america: Hesperonychus elizabethae, a insect and small mammals hunting dromaeosaur from Canada. It's next relatives are the microraptors from asia.
Edit: Yes, this is too a part of my "All Yesterdays" series.