Yes, they can change deed restrictions after you move in (at least here in Texas). There is probably some statement to this fact in your covenants. They can add and make changes as it becomes necessary. If you don't have an HOA or a board I'm not sure how they decide on the changes (that should also be covered in your covenants), but we have to have a majority vote by the homeowners even though our restrictions are handled by a management company and not a HOA board of homeowners. When they make changes they have to send you notification of the changes and give you a set time to be in compliance.

I can't imagine how they can police decorations INSIDE a home, though. Or was that just as an example?

Good luck,
Renee