but then I also had this other 'voice' saying that it might be different if it is a portrait or artwork done of a character not a person.
I think that is a wise voice. First off, I'm not a lawyer, so please don't consider what I'm about to say to be legal advice. But for me, chocolatevampire's phrase "images from the show" sticks out, and I strongly disagree with David that anyone can [display] and sell "portraits of anyone you like" for a few reasons, but we'll eliminate one of the reasons right off the bat (pardon the pun) simply because we're talking about images that can be seen on TV, DVD, etc. So I'll just address the issue of drawing and selling the drawings of copyrighted images and characters.
Copyright law prohibits the use of a copyrighted work without the express permission of the copyright owner. DCP has not given fans a carte blanche to use its images and characters, and you cannot assume that Fair Use applies in this situation. If you create the artwork for your own private amusement, you probably won't have to worry about any actions taken against you for it, but your work will be commercial-- your noble reasons aside (and I think adopting and caring for stray animals is wonderful!!), you said you plan to make some money off the art, and that can be problematic.
However, that's not to say that DCP would enforce their rights. I've seen lots of fanart sold on Ebay too at at Fests and I'm not aware that that DCP has ever done anything about fanart specifically, but that's not to say they haven't, and I don't think you should assume that what you hope to do is legal based on any of this.
To put your own mind at ease and possibly avoid future problems, I'd recommend contacting Jim Pierson and asking him how he feels about it. Then, absolutely do not do not do not flaunt that you got the images from MPI material.
Hope the weather warms up for you!