Progress Report: Cat Retablo

I've applied underglaze to the unfired altar.  These colors will be much less bright after the glaze firing.

What I'm trying to decide now is whether to put an oxide on the background to "age" it a little bit.

When I was young it was the rage among the newly marrieds to make decoupages of old prints, using strong coffee or tea to age the work, much like the effect oxides have on clay work.

If I do use the oxide, I'm going to keep the black and white rope pattern un-aged for contrast.  Would it look better to darken the altar portion to make it stand out more:  what do you think, black or brown?