To be honest, it looks better the way it wasn't originally supposed to be. Extruded outwards instead of inwards. Nothing wrong with changing the original concept if you think it's an improvement.
Modeling in quads or squares is faster and easier, add an edge loop there, extrude that poly-loop, bevel those edges, I couldn't imagine doing that with triangles.
You could try making each one of those an extruded shape (for the overall shape, and not the interior details), and fill in the surfaces with alpha'd stuff for the leafy details.
Add some more detail by splitting some faces, extruding inward and outward, just making the silhouette and the inner detail more interesting same as 2d.
For the chains on the covers, try it in 2 strips in an "X" rather than an extruded cube. Probably knock the tri count down a little and look a little better. :)