There are no easter eggs, per se, but many of the elements that were important to the Barrani High Court in Courtlight are important in Cast in Peril. This is a hard question to answer, because while I could answer it, it would probably spoil the plot in minor ways.
It wouldn’t spoil in any major ways - but some people consider even the subject of the next book to be a spoiler when they’re trying to avoid that information >.<.
I think Cast in Peril might be confusing if the reader comes to it as the first book. On the other hand, I’ve had readers who came to Cast in Chaos first, and didn’t find anything in it confusing - so it’s hard to tell. It’s built, to some extent, on parts of Courtlight because there’s more time spent with Barrani outside of Teela and Tain.