1. Probably not. I'm not thinking about selling these cards in the near future, I just make them in my spare time. I might have to make original artwork if I plan to sell them, but I'm not at that stage yet.
2. No. I wouldn't want to steal your idea and make the same game with my name on it. Actually, I've made these cards for years, way before I had heard of The Past Happened. The originals were all pencil drawn out of card stock I cut out with scissors. I do follow your account, and your cards are amazingly well done, but I did not take inspiration from it for the cards themselves. If anything, your Past Happened page inspired me to put them up here on Deviantart. It's actually based more on the game of War you play with a deck of playing cards than anything else.
3. When I drew the cards, I set a theme cap if you will at 40 cards and then I considered the theme finished. I started with Ultimate Africa, made 40 cards and completed the theme, then I started African Adventure as a sort of "part 2" for the African animals. I just haven't put all the cards from those themes here on the page yet.
4.That's actually a very good idea...I'll try editing the cards to add that detail...
Thanks for your questions and concerns. Again, I just want to restate I did not copy your game at all, though I can't say I blame you for thinking that. Your page just inspired me to put them up, though I've had this game for years. If you have any other questions or critiques feel free to ask, and have a happy Easter!