Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.

I believe the ruling changes depending on the purpose intended behind the art.

Any art that is presented in a sacred context is Haram. For example; drawing saints, angels, assumed blessed people etc. The reason for that is the possibility of people worshiping them or committing shirk in such figures.

Any art that causes harm is Haram. For example; scaring kids, evil eyes etc.

Any art that promote something prohibited in Islam is Haram. Like showing private area, people drinking wine etc.

So in relation to your question, I am not sure of what is the purpose of drawing skulls and beasts.

Is it cartoonish like or scary made for kids? If it was used in any categories I mentioned above or in general something harmful, then it is not allowed.

Same thing to which the art is meant to show life is destroyed. If it was just scenes with no cause of harm mentally or emotionally, it should be fine.

Almighty Allah knows best.