I am making a buttercream two tier cake that has a jukebox on it. It has decorations in black silhouette of fifties dancers on it etc. I just bake cakes as a hobby but I a very artistic and love a challenge. However I am stumped on when start this cake! I am afraid of running out of time and not getting all the elements done in time! How soon can I decorate the cake with buttercream then add the fondant accents without it becoming stale? I am afraid of putting it in the fridge and then adding the black silhouettes made from fondant for fear that the frosting will sweat and cause the black to bleed on the cake! Any suggestions! Thanks!

Unless you use a filling that must be frig'd no need to even think about putting it in the frig. You can bake the cake up to 3 days before OR if you want to bake it up to 3 *months* before and preeze it - well wrapped, of course.
Make up the accent pieces at anytime and store those - covered in plastic - as well.
Then up to 3 days before the event you can start to put everything together.
Doing what you can ahead sure makes it easier on the nerves