The best pictures depend on your marketing. 'Impossibly beautiful supermodel' requires different ones to 'woman next door': the former needs the sort of pictures that might actually harm the latter, because some people will assume they're faked or stolen.
Apart from that, it's much the same as the text: make them interesting. There are clients who only care about price, size, age etc but there are also plenty who care about personality.*
Getting that across can mean having interesting backgrounds or colours or anything else. The two of the three that spring to mind aren't visible any more because they've retired: one YES client had photos in front of rusting machinery / in gardens, and someone else had sets of doing things like the Naked Bike Ride. Both attracted much more attention and are much more memorable than yet another 'here are my tits' one. Another YES client has them in a story order: standing at at open hotel door looking down the corridor ending up with lying on the bed.
As far as face pictures go, 'private' gallery or not, you can assume that once they're published, everyone has seen them and there will be copies around forever. You may or may not be happy with that. Unless you're delighted with it, if you're going to have them, it may be worth making them different in style etc to the more compromising ones: if worst comes to worst, you can deny that the non-face ones are you. If you're not, it's worth remembering that the large majority of people who want to see face pics 'before they book you' are never going to book you anyway.
* The ratio may well vary according to what's on offer: for quickies and PSE, personality is not so important as it is for longer bookings and GFE.