Peter knew that Seth would think he was bullshitting even with the picture, the dude had very little imagination in comparison to himself despite the fact they lived in freakyville, USA. So he reluctantly flew off the triceratops' back to meet his friend. He was totally coming back but he didn't want Seth to come barging in all loud and shit and spook the huge dinosaur. He wasn't in the mood to get trampled under those giant feet. It would be a complete travesty, his face was too pretty to get trampled.
He wondered closer to the edge of the woods and waited for Seth. It wasn't too long of a wait but Peter used his Star-Lord helmet anyway to make sure no other dinos would sneak up on him. The little ones and the triceratops were all he'd seen so far but if they were around, there probably were others too and getting ambushed in the dark was the best way to wind up as something's dinner.
After some waiting, his helmet picked up Seth's heat signature and Peter was proven right about Seth making a bunch of noise when he caught sight of him a few yards away. Even if Seth didn't believe him about the dinosaurs, there was a good chance something bloodthirsty was lurking in the woods and Seth might as well have had a please eat me sign taped to his back. He would have smacked the back of his head if Seth was within arms reach. He couldn't do that but it gave him the perfect opportunity to scare the living shit out of him and Peter was too much of an asshole to pass that up.
He used his jet boots to hover in the air, and he waited until Seth was close by to turn off the boots and drop down right in front of him, the eyes of his helmet glowing red. The look on his face made Peter break out into peels of laughter so hard that he had to lean against the trunk of a tree or risk falling on his ass. It would have been so worth it though.