"I've always liked the idea of Dinos with feathers, and after a little internet research, I learned that T-Rex was likely covered in feathers and that complex feathers likely evolve looooooong before they were used for flight.... and since Chickens are distance ancestors to T-Rex, I was experimenting with giving a Rex the plumage of a wild jungle fowl.
Maybe the tiny arms were wings for mating displays and perhaps fanning for temprature regulation of eggs along with themselves, that coupled with the theory that they were only for grasping mates [since I doubt 500 lbs of presure would be enough to hold any dino still in combat... but it might be enough to hold a mate] led me to imagine that they might be quite colorful [since who would they be sneaking up on, really?].... then there's the Rooster Comb... I was pondering the idea that they were partially, if not mostly, scavengers... so, like vulture, too much feathers on the face aren't condusive to digging your beak [yes beak] in a carcass, so a Rooster comb could serve multiple purposes: keeping the nasty bits off the feathers and making for a terrifying display for any threat [their face looks permanently blood covered]. I also like to think TRex had some sort of head dressing, cuz look at all the other dinos with their fabulousness and horns all on their heads... I don't think T-Rex would be the only one not stutting his stuff. :P"