I was often curious about the unnamed customers. Like the two old guys playing chess.
They were Lars and Sven and will feature prominently in future books. They are there to watch Dresden. Remember how there were other people in the botanical park thingie? That was them, too. And people on the street? Them. People in that other place? Also them. Accordingly, they are also time travellers and also are related to Marcone (who is Dresden's and Murphy's (Mab) son, obviously). They are also Eb's great, great and great, great, great grandfathers respectively. One of them is married to Marcone's daughter (Murphy) in the past when she's Mab. One of them is Molly's grandfather. And, both of them are related to Nicodemus (who is Marcone's time travelling son and Dresden's father (he was a kotc but fell and travelled back in time to found the denarian sect)).
I hope that clears it up for you.