I first watched 30 Rock on a blurry old CRT, and I did not second guess whether or not they would hire someone like Zach Braff for just a quick 3-second cutaway gag. It took until my 8266394th full HD rewatch for me to look close enough to see that is absolutely not him lol
Not just you. I did as well, and apparently it's a common misidentification / urban legend. This Everything I Remember from 30 Rock post from Reddit, years ago, also makes the same conclusion.
I grew up watching American TV, so I do catch a lot of the cameos. But yeah, I definitely miss a lot of jokes and references because I am not too familiar with American celebrities outside of the TV shows that I watched.
That is a neat image! There are a number of things I did not recognize:
Top left, between Paul and Moonvest: Who is that? The hat makes me think of Tracy dressed all pretentiously while going for the O in his EGOT, but that does not look like him
Top center, between Jackie Jormp Jomp and the pager: Who is that? It looks a bit like Rachel Dratch, but there are no obvious features to suggest that
Top center, between Oprah and Thomas Jefferson: Is that Jack on the morning after Kenneth's party?
Center left, between the Tracy Jordan Meat Machine and the Tampa Royal Academy of Dramatic Tricks degree: Who is that?
Center center, between Conan and Lance Drake Mandrell: Whose eyes are those? It makes me think of the closeup of Liz Taylor's eyes, but it doesn't really resemble Dratch
Center right, between Muffin Top and Hey Beantown!: Is that suppossed to be a pair of tweezers holding the troll doll that Dr. Spaceman put in Tracy's nose? It looks like an olympic torch with a flaming baby head
Bottom left, the blue F logo: That remimds me of the Facebook logo, but 30 Rock's version of that was YouFace, which I assume does not use an F as its logo
Bottom center, beneath the text "Gangway for foot cycle!": Is that supposed to be Wesley Snipes's British teeth?