I'm not sure what you mean by "parameters", but yes, it is possible. There are no rules about the origin of the sprite (of course until Cipsoft is able to have all the rights reserved). You can choose one of the proposed sprites by participants during the Fansite Item Contest, you can make it on your own or pay to a professional pixel art graphic designer. The choice is yours.
Goromaphone wasn't a winner place in any contest. Also TibiaTV's admin prefered to choose his own design (Citizen Doll) as well as admin of OrcSearch with their Shield of Endless Search. TibiaBosses in the contest asked only about the idea for the item and the winning entry was to create a Crunor's Heart based on a beautiful story.
I could say, that in my opinion there is no best choice... Contests have their disadvantages. I noticed that the quality of submissions in recent contests is worse than a few years ago. Surprising to me was that one participant made plagiarism from a picture that you can find via Google. Ehhh... On the other hand if you, as an admin, want to create this item on your own - you have to remember that you're not objective about your work. There is a big probability that someone else with a bigger experience can make it better. Well, I think it's all... because I'm already too far from your question :D