When Gwen Stacy died, the Avengers did everything they could to help cheer Peter up. Tony let Peter use his Ironman suit. Steve buys him ice cream, Thor and Bruce tell jokes, Natasha and Clint would just listen to him rant if Peter felt the need to.
Peter Quill actually has a whole catalog of outfits that he wants to put on Rocket, as if he were some spoiled rich cat. However, he likes his organs where they are so he’s never even mentioned the idea of playing dress up.