You don't have to have an expensive and cumbersome four-poster bed to get the luxurious look and feel of one. With a little effort you can make a four-cornered hanging canopy around your existing bed, which will give the effect of a poster canopy bed without having to ditch the old bed. This style of canopy works well with opaque fabrics because they preserve the illusion of the poster bed.
Purchase four curtain rods with ceiling mounts. Two rods should be the length of the side of the bed, and two should be the length of the head and foot of the bed.
Install the curtain rods using ceiling mounts, with screws driven through the screw holes in the mounting brackets. The two long rods should run parallel to the sides of the bed, and the two shorter rods parallel to the head and foot of the bed to create a rectangle of curtain rods above the bed.
Purchase four curtains with eyeholes or tabs for hanging from curtain rods. Four of the curtains should be long enough to comfortably cover the sides of the bed when paired, and four should comfortably fit the head and foot of the bed when paired.
Hang two of the side curtains from each side curtain rail and two from each of the head and foot rails.
Group one side curtain with its adjacent head or foot curtain and use a curtain tie or tassel to tie the two curtains together at the corner of the bed. Repeat on all corners of the bed. This gives the illusion of a four-corner poster bed.