SCENARIO
You're using the Creative designer to build a new creative and when you think it's done and expect to see a thumbnail, you notice that it instead shows up as "DRAFT".
ISSUE
This can happen if you click Save creative on the last step before your creative has had a chance to render.
SOLUTION
Follow these steps to fix it:
Click Edit next to the creative that's showing up as "DRAFT".
Click Next step until you get to the last step.
Wait until all of the design sizes have been fully rendered.
Click Save creative.
FINAL
Your fully-rendered creative should now appear in the list.