Glad to see you around and active,Vrt, I'm happy that you decided to stay and create more art for the game!
Back on topic, I really like the idea, and I would like to say my two cents:
I think it's better to make a permanent or a creature, because they stay on the field and the art will be more visible.
I also think (on their marketing side) that you can take a look to the most used cards (there should be some stats for this, IIRC). This way more people will be interested in donating, knowing that their foil cards will be used often.
Chimera is cool, but not used very often.