Thank you. I did not know this and my place is a mess. Now, as someone who is not very good at using these controllers, how do I "set an object at 0", and then move them using the "x, y' and z coordinates"?
How do I get more weapon racks, book shelves, and chests in my home? It is fully decorated at this point. I need a dozen more weapon racks, and 3-4 more bookshelves, plus I never heard of a mannequin, how do I get one? (Or 5?)
BTW: I am in Whiterun. I don't know if that matters.
Buy a 2nd or 3rd house. You can't buy bookshelves or weapon racks.

@ the OP: If you have issues with Hjerim and you are on PC, check out this thread:
http://www.gamesas.com/topic/1303955-hjerim-house-purchase-depite-quest-bug/
Btw. I like the additions of the bookshelves. Makes placing books so much easier, especially with the new physics of books. I had to manually place hundreds of books on shelves in Oblivion hahahaha (yea yea, didn't use the mod someone made).
But yea, with a bit of patience, you too can have a personalized home! =P I love decorating, even so it can be a pain, since I have to do it twice, because the cell just throws my stuff back on the floor, when I re-enter it. It usually "get's it" the 2nd time around. LOL
Also, be careful what you drop outside. I tried to stash some dragon scales outside the Whiterun house, before I bought it (started a new toon) and when I left to finish some quests and came back, they were gone.
Here's a great thread with some tips on how to keep your items where you want them:
http://www.gamesas.com/topic/1324496-item-placement-in-houses/