Image Banner Dynamic Metaobject - Cannot interchange Objects?

[FlowersGC]

Using the dynamic sources, I'm wanting to be able to have multiple Assets for the Image Banner on my store.

Effectively this would then allow me to interchange the assets as required without going into the theme editor. Set one as Draft, and the other as Active, but it looks like the Dynamic element is not so dynamic and links to a particular asset? 

How can i have it so that I can modify the structure of the code so that the Image banner looks to the active metaobject asset? 

Using Dawn default theme code.