I have been playing a lot of different games all of the puzzle variety.
If you want it to be a puzzle you should not only have various objects to interact with, but there should also be situations that demand a use of an object or several objects. Plus, if you really want to get fancy with it, you could make it so that every thing could be linked in a way. By that I mean use one object to get to another, to get to another, to get to another, etc. Until you finish the level.