Unless you can prove it's a parody, altering copywritten images violates the right of "derivitave works." Copyright holders have the right to keep you from making derivative works of their material, especially for profit. Your only defenses in court would be fair use parody or fair use transformative for "the good of society."
Personally, I wouldn't do it. Make your own images. But I'm not your lawyer, nor would you want me to be.
