I would recommend trying to break the scene up into obviously tiling textures, things such as the floor, walls and so on. Then also create a second set of trim textures you can reuse on certain pieces. You can also make some hero assets that have a bit more character to them. Decal's can also be helpful in creating variety…
you could start by organizing the parts by region, by asking: "which of these objects are Locally owned by the library vs which of these objects are Global to Pandaria?" some textures always go together, like the parts of the pillar and the bookshelf, so they should be on the same sheet. the hand rail is made from similar…