You can get on eBay and see what their current guides say.
As long as the replica itself is legal (as in, something you might buy in WalMart), it should be legal to sell on eBay if properly described.
However, you are likely to run into problems with people getting confused. And not all replicas may be legal. Additionally, some countries (like France) have at times permitted perfumes to be copyrighted, so you could step into issues without being fully aware before you do so.
Do also be aware that you can't ship such things via the postal service -- you're going to have to use things like UPS ground. Given most "imitation" fragrances can already be found pretty cheaply at discount stores, you'll likely have a hard time finding it worthwhile to sell such things on eBay.