These are things that we have expressed interest in but haven't implemented yet. There is no order, if you feel like you can complete one of the tasks. Feel free to fork the project and send a pull request with the new code.
The Flash Clipboard API supports RichText (RTF), HTML, and custom data. We want to enable those as feasible. See Issues #143 and #152.
In a perfect world we wouldn't need ZeroClipboard, and the browsers would just take care of it. We would like to write ZeroClipboard to use the browser's clipboard API when available. See Issues #171 and #105.
We want to setup a unit test suite for the Flash file. See Issue #43.
Most of the API will be redesigned for v2.0.0 (as we did not design the v1.x API but rather inherited it. Feedback on the [https://gist.github.com/JamesMGreene/7886534](ZeroClipboard v2.0.0 API draft) is welcomed!