Can you add an "On Hold" or "Pending" status?
Sorry, but in our experience, putting an issue on hold is counter-productive because it's easy to forget about it. We do, however, have some suggestions on how to adjust your workflow to help you work effectively without putting issues on hold.
Another option, and the one that we use internally, is to create a separate project for handling issues that are inactive or pending. In our case, we have a project called "Ideas". In many cases, issues begin their life in the Ideas project, and when they're ready for prime-time, we'll move them over to the main project. This ensures that our primary issue list isn't cluttered with a bunch of pending ideas. We have a whole blog post that elaborates on how we use projects to stay organized.