I promised my players something special for their 3rd session, so:
Since the Isle of Dread was inspired by King Kong (especially the Tanaroa gate where the lair assault occurs), I replaced my normal BBEG miniature with a special King Kong miniature for the occasion.
The players' surprise was completely worth it. With a captive female Druid in hand, Kong climbed to the top of the obelisk and started dishing out the hurt while flying creatures buzzed past him. He even tossed a couple of barrels at the PC's. The night ended with Kong rolling double-crits (72 HP of damage) in a single action on the last PC standing
For the next session, I'm considering describing the BBEG as a Lost
style Smoke Monster (since many similarities have been noted between the Isle of Dread and the Lost isle).