Pictures are just snap shots of the event/moment... so when someone comments that he looks freaked out, they are responding to his body posture, ears,, and whale eye. The pictures portray a puppy that is a little overwhelmed by the other dog. Honestly, even if he was having a blast, that doesn't seem too far off because he is just a puppy and he's in the company of older/bigger dogs!
I would think as long as everyone is truly having fun, then all is well... just be careful. I'm not really a fan of dog parks
Murdock - GSD
Virgil, CGC - GSD
Tara, Reagan, Madison, and Jefferson - Aussies
The birds: Dante - CAG / Nero and Sunshine - Budgies