Much of this work has actually been done for a long time: selecting cardbacks, royalty images, and window backgrounds is all already working. But the user interface for the Decor window, where you can select these things, was clunky and hard to use. I spent some time on it, and I think it's better now.
By the way, there's one feature from old Solitaire Till Dawn that won't be in the next release: you won't be able to create cardbacks using your own photos. I'm sure people will want that, and it will appear in a later release. But right now I'm focussed on getting a usable release out the door and into your hands, and custom cardbacks would take too much time to implement. (You will be able to use your own photos for the window background; that's already working. Cardbacks are harder because they're small, so you'll want a nice user interface to scale and crop your image so that it fits nicely: that's the hard part.)
I am now adding the old sound effects to the new release. This is another feature I might have skipped if it would have taken very long to do, but Cocoa makes it dead simple. I've spent just part of today on it, and I'm nearly done already.
Update October 11 2013: I am retaining compatibility with Snow Leopard (Mac OS X 10.6.8). Everybody who wants the new version but doesn't want to upgrade to Lion or Mountain Lion, y'all can relax. And thanks for the feedback!