Is there any list of the items which can be "open"/ changed into new (random) items?
I know about few of them like, however, I am sure there is much more:

You see a shiny stone.
Something precious might be sealed in it.

You see a surprise nest.
Use it to get a little surprise.

You see a medicine pouch.

You see a surprise bag.

You see a surprise bag.

You see a surprise cube.
There might be something valuable inside.

You see a surprise jar.

You see a gooey mass.
Perhaps it contains something useful.

You see a lot.

You see an unrealized dream.

You see mysterious remains.

You see a gnomish supply package.