I remember reading about the same. Since lava's temperature is well above above the Curie temperature of magnetite(800^(o)C), and it cools down, the orientation of the magnetite particles are all aligned and proportional to the ambient magnetic field, which makes it ferromagnetic.

Sight is the last sense to go
Brain is the organ that survives the longest amongst all other organs
In short, you turn pale; all the blood in your body settles down on the area closest to ground creating bruises; then body goes cold no heat signature; then rigor mortis sets in i.e. your joints become rigid and position of body cannot be changed; then all organs in your body liquify and bloat your body from inside with fluids and gases; then you start decomposing with scavengers of the the society like maggots, insects and animals feeding on you and breaking you down until you turn in bones

You can make the details of the creature less distinguishable, to give it an imperfect state, which would look real. Like the eyes and the spaces of black left are too crisp. Diminish or shade them in to make it look real.