Pimpdawgy;
In the mirror image room you can break all the barrels, etc to make it easier to try to spot the difference. You don't necessarily have to spend all your time examining the ground...
straight ahead from the entrance, where the chests and chairs are, take a look at the top of the half-height wall near the chairs.
singo;
The dragon scale is on the path to the blood alter, where the dragon is. Read the book when you get it (the one the librarian wants, though that is optional, and the second volume he gives you in return); you don't need to do so at the alter.
