I don't think the houses are too boring, and they've certainly gotten more interesting after Celestia. I do think they should add some new houses for Azetca on. And, excluding the Sun Palace, we never did get a Zafrica house.
I agree there are plenty of house options. I'd like to see more furniture, wall hangings especially. I'd definitely like to see a buyable or craftable portrait of Belladonna Crisp. :) And quite frankly more portraits of the various characters in general. For example, all the School Trees would be nice. There are so many cool characters in the Spiral, it would be nice to have portraits of them in our castles. Busts and statues would be cool too.
I usually go with themes, my has the Death house and trying to get the Wyrd house, and like Von said (wrote) there are a lot of houses to choose from, and different methods of obtaining them: crafting, crowns ( can buy with gold), gold, or from Gift Cards. Not to mention their probably going to be a lot more houses in the future .