IruP:

I'd add:

• Error Checking: You're currently assuming that some parameters are passed, but not enforcing it. So when an error occurs, you don't know what's going to happen. Any changes to the MongoDB class won't be reflected in your own.
• A test suite: You ought to verify that your library works as intended so you don't get surprised.
• Make it do something: Currently it doesn't provide any functionality not already provided by MongoDB, so what's the point of it? It renames a couple of functions, but that would only make it a little harder to use, since users of MongoDB would expect different names.

As a learning exercise, it seems like a decent start.

...roboticus

When your only tool is a hammer, all problems look like your thumb.