For me, the daily world's nature is in my eye, the imagination is not the finished piece, how the image is lit and composed can make or break the digital art. A beautiful picture can look like crap with poor ingredients and skills. But a slapdash picture can look great if it's created as a painting. The concept is the heart and soul of an illustration, if you don't have that as a foundation, the illustrators are trained at colleges directly in front of the screen, most are merely made aware of the technology available and expected to train themselves to utilise it.
An Illustration is a visualization such as a drawing, painting, photograph or other work of art that stresses subject more than form. The aim of an illustration is to elucidate or decorate a story, poem or piece of textual information (such as a newspaper article), traditionally by providing a visual representation of something described in the text.