When the art made for Magic is reduced to that tiny rectangle you're used to seeing on cards, some neat little details are lost, or at least shrunken to the point that most players don't notice them. The little person on Mirage's Phyrexian Dreadnought is such a detail.
The Dreadnought, illustrated by long-time vet Pete Venters, was at the time the largest creature ever in Magic. To show just how big it was, Venters painted a human wizard in the lower right-hand corner casting a spell at the massive hulk.
This nearly full-sized version of the artwork allows for easier viewing of the hidden little man.