Hi Andre,
I'm not very familiar with the protocols that printers use, but if the connection is simply over a TCP or UDP connection, then sure, that should be no problem. However, if you need to do some sort of upper-layer fixup, then maybe not. The CSS only really has application layer capabilites for HTTP, and just enough for FTP to open the necessary pin-holes, etc.
So the bottom line, is if for printing, a client simply opens a TCP connection on some port to the printer, sends the print job, then closes that connection, then i don't see any reason that the CSS, or any load balancer, couldn't load balance it.
Perhaps you are more knowledgeable on printer communications than I. Are you aware of anything special that might make printers tricky to load balance?
BTW, I think this is the first time I've heard of printer load balancing. Learn something new every day! ;- )
Sean