Most definitely. The ssi_recentTopic() function already lets you choose which boards to exclude. However, there are several topics that do this already. Renegd98 has posted one of them.
Here's an example of the ssi you could use if you wanted.
ssi_recentTopics(10, 5, 'echo');
10 = number of topics displayed
5 = board ID that you want to exclude (you can exclude multiple boards by using an array)
echo = default to echo out the topics