I will say, I think too much has been made of the "death wall".
To me it looks like something that the kids drew. EP probably knew she would soon be selling the house and they would have to spruce the place up before putting it on the market. So, she may have just told her kids they could draw on the walls since they'd have to repaint.
There's also been a lot of speculation about the imagery and words relating to death. One tradesperson said “You’d think they’d be drawing flowers and unicorns, not gravestones and death”. But, IMO, that's ridiculous. Whoever said that knows nothing about childhood development. EP's children were right around the age where many kids become interested in the macabre. When I was that age, some kids would litter their notebooks with drawings of skeletons, gravestones, coffins, blood, etc. Some were obsessed with horror movies, death metal or other pop culture with gruesome imagery. There's a whole "goth" subculture that's a reflection of this interest. For most kids it's just a phase that they eventually grow out of. Despite all the speculation, I don't think it's an indication that there was anything wrong in EP's household.