painted+color

[sandokana]

Hello everybody!!
One of my students wrote this sentence which I think is wrong..

"My room has walls painted purple..."
I´ve never heard about this structure... and most of them were with verb to be (not have)
Anyway, I have these possibilities:
1. The walls of my room are purple.
2. My room has walls which are painted (IN?) purple. (Although this one doesn´t sound natural to me)
Can anyone tell me the proper explanation about why the sentence of my student is not right?
Thanks in advanced!!!

[Joe]

My room has walls painted purple...

is possible by reason of ellipsis and actually means

My room has walls that are painted purple...