Upholstery and egg crate type foams will not be rigid, and may not be flame retardant. EPS and XPS construction insulation foam are lighter weight, more rigid, and could be covered with batting and fabric. They come in 4'x8' sheets, but can be cut with a utility knife into smaller sizes. They are available from a big box home improvement store like HD or Lowes. Not sure if they are flame retardant. Depending on how large a piece you are mounting, I would think they may be light enough in weight that they could be mounted to the wall with 3M removeable hangers of some sort.

Ok. in that case please let the area dry in summer. It is very important. Remove the area mould completely with power washer and bleach. Do it for 2-3 times. Do cover the area with " Damp proof " smart care solution and then use "Ultima Protek paint" . The products mentioned above are from Asian paints . I am not aware if similar products are available in other brands. Please use your discretion. Thanks Nitin Cornerstone Designs Bangalore.

Can you share the pic to gauge the damage.

Simple! Avoid paint! Simply buy 2 sheets of laminate (one for front and back each) that matches with the rest of your doors, and paste it on the PVC door using a strong adhesive (HeatX by Fevicol, or any other alternative). Enjoy! (Note: This solution can work only if there are no undulations on the peripheral frame of the door) I hope this was helpful.