There will be tiers in beta for all classes, yeah.
Not just for prostitutes alone, all classes will have tiers.More tiers for important jobs (like prostitute) and less for minor jobs (for example cleaner). I think about 10 for the former and 3-5 for the latter. This allows us to use complex and interesting logic, and also balance jobs properly.
But if we go that way with clothes too, all job will need multiple versions of clothes depending on average tier level, not only prostitutes. At least two versions for minor jobs and three for important jobs.
Which is achievable too of course, but will take huge amount of time and even more imagination. If you really willing to render that much, I propose to expand packs post beta
Also, prostitute job by itself doesn't have a special tag. This is because such pictures are very rare indeed, I mean when you can look at the picture and realize immediately that it shows a prostitute. So we simply show sex scenes, assuming that customer already hired the character.
In case if we'll ever need to show prostitute job without sex, it probably just will be underwear.