You cannot encrypt your items yourself as far as I am aware, however the store will have an update that will encrypt every upload if an artist wishes, to ensure that assets are protected.
This will be in sometime early next year.
Items encrypted will indeed feature a message stating they are for use in reloaded only, you will not be able to encrypt existing items as purchasers of those items will have paid under the agreement they can use in any engine and the asset would not be encrypted.
Windows 7 Pro, Intel i7 3.8 GHz (Passmark: 9021), 16GB DDR3, NVIDIA GTX 780 4GB Superclocked (Passmark: 8056)
