If you have a (preferably NVIDIA) GPU, you could run one of the many applications that use Stable Diffusion on your PC. I have only used these before:

Fooocus: Really easy to set up, but not really meant to be used with other custom models, has lots of artstyles to choose from.

Automatic1111: Also pretty easy to set up, maybe a little bit harder. You have to download the models from somewhere else, but its much easier to import them and it has lots of options.

Fooocus will probably suffice, just select a fitting art style to get a good look.

Ok, thats a bit different, if the house is somewhere where noone wants to live anyway (and if they want there are enough options available), then it really is ok morally, at least for me.

One could argue that the space should be used for farming, but that depends on how big the property even is if that makes a difference at all.

If it has a really big property with lots of grass it would be a good thing to rent that part out to a farmer. If it is more of a forest its probably better if it stays that way.

I would say owning it while not using it very much and not renting it out is the least ethical choice as no one can use that house.

The most ethical option besides not owning it is renting it out at a reasonable price, so someone else can live there and you are not squeezing every last dollar out of them.