You shouldn't be creating anything specific to this jam prior to this jam starting. But you can use previously-made content (either made by yourself or by others) that wasn't specifically for this jam, as long as you mention what you re-used when you submit (so that others can rate your game fairly).
So in answer to your specific question: no - but you could treat it as a separate game and just re-use things from your previous game (if you mention these things upon submission in the appropriate text box).