ACtually, the issue w/ papparazzi is that if it's a "public figure" in a "public place", and you get a shot of them, it's legal, it's yours, and you can sell it. If you're shooting Kid Rock in a concert, then fine, it's your shot to use. If you've hired a helicopter and are shooting Britney Spears with her new baby in their own back yard, no, it's not legal. Basically, if it's someone you can recogzine from the media, and it's in a public place, you're good to go (if you take the shot yourself), but if all that is not met, then no, you can't use it.
As for the written word, if someone else has published it (and yes, on a webbie is publishing in this regard), then you need written releases from the author, the publication, and the interviewee before you can be safe.
If you took one of my photos, and painted something from it, you bet I'd be angry; it might be a judgment call in a courtroom if you based your painting on my photography without my permission, because my photo has releases, is my own creativity, and my own post processing; you're simply altering the final output.
However, if you have a shot from which you create an entirely NEW piece, then it's yours. It's a terribly fine line, and the courts tend to side on the original artist's work as a protection for future law...but I've heard about cases going both ways.
Good luck - it's an interesting and really creative idea...but get your legal ducks in a row before you move into the creative vein, because that's what can hang you up faster than a noose.
(And BTW, what I've stated is only for the United States...)