Displaying larger stuff can be very tricky, especially if you have a lot of it. Since you have already kindly commented in my 'Building A Display Cabinet' thread here http://starwarsforum.co.uk/viewtopic.php?f=2&t=36404
, you'll probably guess that my suggestion would be to calculate what you want to display and how much space it will require, and then try building yourself a bespoke cabinet. However, I appreciate that that option is not to everyone's taste, and some people might be a bit daunted by the prospect of a DIY job and hence be reluctant to try.
If you do decide to give building one yourself a try, I am more than happy to offer advice if you want any. Or alternatively, depending on your funds, if you'd rather not try building one yourself, you could always see whether you could find a local carpenter to build one for you.
However, displaying a loose Death Star (I'm guessing Palitoy, rather than Kenner) poses a special problem all of its own, as it is far wider when assembled than any vintage box. Have you considered looking for a large glass topped coffee table with a shelf or space for a shelf beneath the glass? You could display the Death Star fully assembled and have it be the centerpiece of your room all at the same time. If it was me and I was plumping for this option, I would want enclosed glass or wooden sides on the lower shelf as well to help protect the toy (if glass, it would of course need to be toughened, like the top of the table would be). And again, if you couldn't find a suitable one to buy, you could always try building one yourself or having a carpenter build one for you.
Here are a couple of Millennium Falcon coffee table pics I've just shamelessly stolen from Google images to show you the sort of thing I mean:
Good luck with whatever you decide to do, and keep us posted on your progress!