Help is always wanted. If you have a BitBucket account its easy, click fork and hack away!
Please attempt to follow my suggestions that I list below though, they will make the process less painful and we will hopefully end up with a reasonably intuitive interface in the end.
I highly suggest asking on the list-serv first if your work is going to be useful to the project.
CuteHg is meant to be used by people relatively new to the ideas behind DVCS. Few assumptions should be made.
Your first step should be "What do people want to do and what is a friendly way to provide said functionality?" This does not always mean "what do I want to do, and how do I want to do it." While you yourself are likely a user, you aren't the only one. Keep in mind someone might be unfamiliar with terminology. Your average user is not likely going to understand what a DAG, diff, merge, push, pull, clone, etc are. That is both a mental picture and terminology a person has to build up to with the help of examples and good simple descriptions.
I have been using a top-down approach to developing CuteHg. By that I mean I think of interaction first, gui second, and code last. Its a failing of many GUI programs to begin bottom up. No user will care how good your code looks.