What about copyright, in the sense of "creating derivative works"?
If they're for intended for your personal enjoyment, at home, that would be okay. Visitors can see them and it's not as if you would charge them a fee, so copyright people would not make a fuss about that.
You mention a website and make it sound like it is a commercial concern. By using famous faces you could be (unintentionally) implying to impressionable customers that you have personaly hob-nobbed with these celebrities (actual sittings) and/or that the celebrity endorses your work. They will likely be dissatisfied to learn that this is not the case and express this to their contacts, even though the misapprehension is entirely theirs.
If/when the celebrity has the website brought to their attention, they might take issue with the unauthorised use of their image (their 'brand') without prior permission. It's all about 'control', or some such *****cks.
Oh and the photographer who did the original shot, or rather their lawyer, would be interested - gleeful even - too, to have such easy access to evidence of a breach. You'd make their day.