There are several approaches that you could take in writing the conclusion to your research paper other than to refer back to your introduction.
You could summarize your main points but if you use this method then be sure to make your summary interesting rather than a just list of points.
Present a bold statement that takes your topic to a deeper meaning and state the overall importance of what you have said in your paper.
Conclude your paper by restating what you have found, acknowledge that there is more to be explored on the topic and briefly describe the issues that remain.