You can certainly create a 144-node cluster, just as you can physically.  Since this is VM, however, you will probably be limited by the memory in your ESXi server.  Each VM image comes default at 1 GB RAM but truth be told runs better in 2 GB if you plan to do anything non-trivial with it.  So just to hold 144 VMs you'd need ~300 GB RAM in your server, minimum.  Hope that helps. Have fun.
Hi folks,  What's the biggest virtual cluster I can create? Thanks!
Maximum Virtual Isilon Nodes