you don't really make money selling cards. on this site i make $15 - yes they frame them, who knows why else they would spend that for a card. you'll make more with prints however. you can mark a card at any price you want on any store, but it may never sell. most sites sell cards. i would never use GCU - not ever.
this site isn't really set up to sell cards, it's a place to sell prints. so message cards may not do that well, and it's hardly worth a dollar profit.
i do recommend though that you drop the copyright death threats on each one, that is a sure way to annoy customers. you may want to look into better fonts as well. also black on brown is hard to read.
you have very few keywords, if it was a poster there is a chance at more tags. ideally i would focus just dropping the words and selling things as prints. but there are other pods we can't mention here now, they all sell cards. but again, they don't sell well because you can get them cheaper from hallmark and get them right away with no shipping.
---Mike Savad
MikeSavad.com