It would be safest by simply creating a paper wallet while offline, and rebooting before going back online, then transfer the tokens to that ETH address. Done, secure vault... It's very easy. I like to fold & laminate several of them with simple clear parcel tape so sealed tight (keys hidden inside and waterproof) and I enjoy the idea of having totally secure exclusive access from a handy qr code in my wallet or in a safe place. In this way anyone can carry an endless amount of assets around and across borders with no cash or electronic equipment, no bank check to deposit or wait on clearing in a foreign country. Try getting on an American flight with 20k cash or more sometime... hehe.
Soo Cool that ICN will also have visa debit card access! Noting though that part would indeed involve site security. So yes with that in mind you CAN store them there, and just use the debit card to reduce your shares and asset wealth on sucking down an Starbucks over-priced frothy-Latte' hehe.
Future Comment: "Help please... I went to the Lambo dealer with my founder's club debit card and they told me the green one was over my daily withdraw limit, what to do?" Answer: Buy the red one and trade it for the one that "Chase" has. (other ICO participant) Chances are he left a kilo or two in the glove box.
There will be step by step tutorial of how to manage ICN from Mist. However, that is not something for newbies in crypto world - still too complicated for them. Might be hard to believe for you, but is true.