I've spent some time on the Nautilus Metadata Tile, as I had a few ideas regarding the UI. I can't go over the top with the colours and effects, as I hope one day this can be accepted into Nauitlus main. However, I have messed around with GtkStyle & Cairo, and have come up with this so far:
As you can see, I have just done a simple gradient between the base[GTK_STATE_NORMAL] and bg[GTK_STATE_SELECTED] from the active theme. I think it works quite well in practice, and doesn't 'steal' the focus away from the main icon/list view.
I have also added a GTK_STOCK_EDIT button in the bottom right, clicking this will swap the tags GtkLabel, to a GtkEntry, so you can edit the tags.
I also got round to adding some of the other tiles, and some icon/thumbnail support. Below are some screenshots (with different colour schemes to show how well behaved the gradient is ;).
As you can see in the Image tile, if an image has data about the camera/camera model, the title will reflect this (don't laugh at my camera model ;), exactly like what happens with a music file.
I still need to add the document tile, but I have left that till last because it will have a snippet of the contents, and I need to decide on how to present this!
I am still making code changes, so if you have any more ideas, or want to add anything to the tiles, let me know in the usual ways.