Charles, all my books in Mantano are put there by CC. I don't import books into Mantano independently. So I assume it is getting the information from the book's OPF.
And, no, Mantano can't show images. I was curious about that feature in Calibre so I tested it (never used it before today until you brought it up), and web images inserted into the comments section will just show up as a URL on the book details page (same as with CC).
Again, centering is a relatively minor issue for me, so no problem if it's not something you would want to pursue. CC is pretty awesome as it is. But .... if perhaps one day you had a little extra free time, maybe you can think of a way to easily implement it within the detail page's existing structure.
--Pat