Sources close to Khloe tell TMZ ... she had extravagant renovation plans for her Calabasas crib -- the one she bought from Justin Bieber in 2014 -- by turning a bedroom next to her master into a closet big enough for her massive clothes and shoe collection.

But, life happened. As TMZ first reported ... NBA superstar BF Tristan Thompson knocked up Khloe. So, that bedroom-turned-closet is going back to bedroom ... baby bedroom.

Khloe wants the baby's room as close to hers as possible, and that room's the perfect fit.

We're told Khloe is holding nothing back when it comes to the fine details of the room ... buying top of the line furnishings, decor and clothing.