There is a thread by Siam here:
EU will execution which includes information from support cases about this issue.
In summary:
1. Make a legal will (you should do this to cover your RL assets in any case). In your will, you will appoint an executor.
2. Your assets in EU form part of your personal estate to be managed by your appointed executor. If you want some person other than your executor to be appointed to manage your EU assets, I would suggest you keep a written
codecil detailing exactly what you want done with your EU account, and naming the person you want to have do that together with their contact details. After all, if your executor is your husband/wife, and they're not a gamer, they'll need help in chipping out your avatar etc.
3. When you die, your executor will need to contact MindArk, providing a copy of your death certificate (to show you're dead), your will (to show he's the legally appointed executor), and the codecil (if you have one). MindArk will then give them access to your account, so that your instructions can be carried out.
Note: MindArk may agree to assist with creation of a memorial, but only if that's requested by the executor, and that if you want that to happen, I'd suggest you mention it in your will (or codecil).