Google Calendar has the option of being customized by enabling features under the "Labs" setting. I would like to make my own customizations similar to these Lab features. Is this possible?
Unfortunately no, users cannot add their own labs features to this list.
You can however suggest a labs feature, the link is provided on the Labs page: http://productforums.google.com/forum/#!forum/calendar
Not sure how often, if ever, they check this, but you cannot add a user-generated lab.
You can develop your own "gadgets" though: https://developers.google.com/google-apps/calendar/gadgets/sidebar/?csw=1#developing - they give you limited access to specified areas. Not full access as we'd all hope but perhaps enough for certain projects.