I also wouldn't want to see postcards in a category with stamps.
Not sure I will be popular for saying this, but I don't really see much benefit from moving the postcard category from where it is. Every single postcard buyer on eBid will also have a bay account and therefore they know exactly where the postcard category is located. 99% of the time a new postcard buyer comes to eBid it will be via a listing on Google Organic or they pick up an eBid adword on google, I would think the amount of postcard buyers who manage to stumble upon eBid and then start to search for the postcard category is negligible.
If it is ever moved then, as per Bunsock's previous comment, there would certainly have to have a ghost cat in the present position under collectables.