Re: Decrepifying a Beautiful house
cut out the house and land and put them on a new layer then put a new sky tone underneath it. I'd suggest something along the greys and puke greens.
As for making the flowers seem less lively, experiment. Maybe burning the pedals or changing the colour to browns and such to "kill" them. try using effects that make the pedals look like they've curled up if you have time.
On the house try making the paint look like it's peeling, shingles have fallen off. broken windows or boarded up windows. etc.
Then follow it off by essentially makign everything look realy grungy and dark.
