What about this stuff for laying out the palace?
http://gcmini.mybigcommerce.com/spacecraft-interiors-25mm-30-mm/It's technically intended for sci/fi games, but it is so plain that I think it would be easy to make it look Egyptian. The floors could be painted like tiles, the walls could be painted or have printed murals could be pasted on them, pillars could be added, or half-pillars along the corridor walls, etc. The pieces allow for secret passages - did you notice that?! The larger areas might do for the garden or throne room or main harem area.
I think they are probably stackable as well...