Hi,
I've done several similar illustration commissions that place real people in comic book covers-- there's an example ('super-hero family') in my Freelancer portfolio.
And because I'm a pro illustrator, working mainly in comics and videogames (previous projects include Spider-Man, Justice League, Reservoir Dogs, Barbie, Doctor Who and SpongeBob Squarepants), I have lots experience at this sort of illustration.
I start by creating a digital 'rough', based on your description and the photo reference you provide. When you approve that, I draw the black and white artwork on art board in pen and ink before colouring your illustration digitally. You'll get to see the artwork at every step of the way.
If you'd like to see more of my work, my website is easily found by searching 'Stephen Baskerville comics'. If you have any other questions please let me know.
Thanks,
Stephen