Personally, I think there is nothing wrong with "just" dialogue, as long as it doesn't throw the reader out of the situation. But you could add more thoughts of the characters, how they see the actions of the others and how they see the situation. You can also do a lot with gestures, like tapping the fingers, playing with a wedding ring...if you write about Neal in the office, he can always play with the rubber string ball (for fanfictions it's always a good idea to keep attention to the habits already there...Peter is frowning a lot, so I like to use the word for him although its very much a standart-word, but it wouldn't fit Neal or Diana).