Unfortunately there is no easy method that I am aware of to emboss an image. If the "artwork" was done as a vector graphic I have had some luck in the past exporting it out of Photoshop or illustrator as an .eps bringing it into AutoCAD, doing some work on it there, saving it as a dwg, and then importing that dwg into a sketch in Inventor. Sometimes it works, sometimes not, just depends on the original image.
There is a "decal" function in Inventor that is pretty simple, but it is just that a decal, there is no depth to it, and you cannot use it to create an emboss feature.
Most times with just a basic silhouette type image it is faster and easier to just draw it as a sketch in the model. You can use the image itself and trace over it in the sketch, makes it go pretty fast. I drew up the boxy guy and embossed it in about 5 minutes - the grill part would take a little longer since it would require splines and what not.