Green_Hilltop: To be honest, that thread isn't actually a giveaway but a contest. You're basically asking people for a commission of your character, and instead of paying them, you're offering them games that you got in a bundle (so basically you're paying less than a dollar for it, since it's Humble Bundle games like you stated), given that you don't even state that the winners will be raffled so I'm assuming you will pick the winner based on which drawing you like the most. So like Sachys said over there, it's no surprise that no artists have entered the contest.
However it's good that you've done some raffles before and if you check your thread now, it's high rated again, so it doesn't really fluctuate that much. If you'd really like your character done though, and have it be a good quality drawing, I suggest that you just ask for a commission here or over at DA/Tumblr - the going rate for a basic character without a background is usually five dollars or more (or at least used to be), and you'll get the full rights and everything like you wanted, and you get to support the artist. :) Hope that helps!
You're right. When I did previous raffles, I did one as a simple raffle, then another as a first come first serve. Focusing on the
variety of my giveaways, I did a drawing contest this other time. Basically I didn't like following one system for all of my giveaways, and thus this contest was born to fit in with the variety idea I have going with the giveaways. I should be careful next time in a drawing contest.
But otherwise, what I'm worried about is that there is a fluctuation on contests such as this. Even if its like a paid commission as you have stated, both sides would have fun and enjoy the contest. Downrepping the contest's main thread instead of taking the time to put a post regarding this thing is just off to me. That said, I should really look into revising the rules for it.