Im Windspirit
You'll have to make a request in the Update Shop for that. That is not true. If it was a mistake by the artist then he or she can change the art without needing to go to the Update shop.
I'm sure it was a simple mistake and this applies to contest digimon as well. If the person who won said digimon would like to have a different sprite or have a different avatar used then he or she has the right to PM the artist to change the art. This was confirmed by Dstdnt.
The scenario above applies for digimon in the TP shop as well. It would have been different if I didn't mention giving Shoutmon a nickname, but since I specifically made the request to have my digimon be called "Stannis Baratheon" then the artist should make the needed changes.