Is there a list of common tags for adding memories?

tags are really only helpful - for people who actually SEARCH by a given tag

and we dont know ahead of time - what people will search on.

They are apt to simply search on a keyword that comes to their mind.

So with that in mind - you should simply add the tags that you feel most aptly describe the item.

BUT you should be aware that many people are not even aware they can search by tags - and thus - I would not go overboard on a search option that many people are not even using.