Really! I always thought the "rule of thumb" was use as many dowels as the are inches in the cake that will sit on them. I don't use That many but if I am setting a 12" on top of a 14" I will use more than 5. At least 10 dowels. I use pvc for dowels, not wood. I am too paranoid to use the bubble tea straws!
What size were the tiers? If they were large, 5 dowels in each tier, (especially the bottom tiers) does not seem enough to support such a large cake.I use 5 dowels under and 8" cake. I'm assuming the bottom tiers were larger than that.
I don't want to burst your bubble but fondant on top of cream cheese may be a disaster in the waiting. In my personal experience, the fondant started to melt and slide right off the cake.
Reseach this site for the posts and you will see that it has happened to many many many of us!
I never trim. If I feel the edges are too crisp, I wrap the cake in Plastic wrap 10 minutes after it is out of the oven. The cake will "steam" in the plastic and after a few hours or overnight, the edges will be soft. Plus the steam boosts the moisture in the cake itself.
I would just make a gumpaste or fondant plaque. Then I would use clear tape and cover the back of the printed image and stick that on the plaque with buttercream or piping gel. The clear tape would serve as a barrier so the image won't get greasy or spotty from the BC or gel.
Obviously you would tell your customer that this is not edible and to remove the whole plaque before serving the cake..