QUESTION: Is the life post liberation as per the philosophy of Advaita-vada kind of Ghostly?
Ghosts are entities who are blocked from taking their desired form. They are riddled with incessant unfulfillable desires. Existence in Brahman is nothing like this at all. It is nirvāna and śānta – without disturbance and perfectly peaceful. There are no desires whatsoever, and a resultant natural sense of happiness (realized as peaceful tranquility).
QUESTION: Could life in Brahaman be like being a contended, happy ghosts.
Ghosts (even a content and happy hypothetical Casper) are discrete entities with a sense of identity and desire. There are no discrete entities in Brahman, no sense of individual identity, and certainly no desire. Existence in Brahman is incomprehensible and indescribable. It cannot be made analog to anything in our experience, certainly not to ghosts.
The best description I can imagine of existence in Brahman is absolute, unlimited peace. This comes at the cost of having absolutely no individuality and ambition or desire.
Prema is infinitely better than Brahman, but this doesn’t make Brahman equivalent to being a ghost. Sometimes a prema-bhakta may denigrate Brahman out of emotion and love for Bhagavān. but this is a bhāva-vicāra (a subjective angle), not a tattva-vicāra (objective angle). The objective angle is that Brahman is a partial comprehension of Bhagavān and therefore is glorious, though everything that Brahman offers is merely a subset of what Bhagavat-prema offers.