How do you do that?
The art work is made of sugar paste or modeling chocolate.  Usually pieces are sculpted by hand but molds and cutters are also used.  Some pieces require toothpicks or wire for support.  Eatable wafer paper is used for delicate items like butterfly wings.
Is the art work eddible?
Technically yes (except for the wire or toothpick supports).  However other than the modeling chocolate it is not very palatable.  
Where do you get your inspiration?
My inspiration comes primarily from the person for whom I'm making the cake.  My garden, the wonders of nature , works of art and textiles all influence me.  I also try to infuse a sense of humor when appropriate.  
How do I preserve my cake topper?
Your piece will last for years if you keep it away from direct light or humidity.