Basically everything you can imagine (and more) can go wrong.

Without any further information (e.g. what you define as "safe"), no one will be able to give you some useful advice for a specific software/hardware.
There are lots of attack vectors, it depends on which of them apply to you. Based on this, there are good and bad decisions for your case.

Generally:
No closed-source, web- or online wallets.
Your wallet can only be as secure as the system it is running on / the building it is placed in.