Not sure if this idea has been suggested before. Hopefully people aren't too upset at the idea, as it could create a bit of a cash grab.
Create a free furnishing for everyone which depicts a representation of the number of Crowns your account currently has (Fable 3 had an amazing example of this)
This could be in stages (e.g. 100+ is a small pile, 1,000+ is a bigger pile with various trinkets, 10,000+, is a full chest, 30,000+ is at dragon hoard level, etc.) though the more detail, the more popular I would expect it to be.
This would mean that people would buy Crowns, just to show off their Crowns, but it would also create a fantastic looking furnishing.
The added advantage to this is that by creating this mechanic, it could be relatively easy to create a similar mechanic for other currencies (e.g. gold, transmute crystals), which the stockpilers would absolutely love.