There use to be an option when you clicked on availables/tbr etc that you could click to see only the books that you actually have, as opposed to books that have more than one journaler for so that you didn't have to scroll through the whole list. Has that disappeared too?
When I release a book, the count (4 weeks and all time) increases, but the "recent book activity" never changes. The 3 most recent ones that are shown, have been there for weeks.
Try registering rather than releasing a book - then you should get some new covers :-) Although it says Recent Book Activity it actually shows the Books On Your Bookshelf Most Recently Registered, whether by you or a previous owner! Plus, it's probably best to register the long way round if you want to see some changes. I've seen comments that at present using pre-numbered labels doesn't alter the covers because they date to when they were printed not used but I never use them myself so don't know! Your stats suggest you've registered thousands of books but none in the past 4 weeks, possibly not since the site changeover i.e. the start of the book cover scheme