Let's me know you put work in yourself.  BUT if its candid and the price is right then...

Well posed and lit, and reveal your assets honestly.  Also, they should blow up to a decent size, not just a few inches across.

If I had a nickel for every bad photo I've seen, I wouldn't have to worry about work.

unless you don't have access to a decent camera or a buddy with a little tallent.
Digital photos can be so good...  cheap to shoot a bunch, to pick the best.  NO cell phone shots.  Decent resolution.  As previously suggested, Opens so they can be seen properly.  
Don't get me wrong, photos are VERY important.  I click off low res/fuzzy/thumbs only in a nano-second.    But photos need to be updated fairly regularly...  why spend a bunch of money unnecessarily.  
You want to attract me.  The photos should be a fair representation of your current appearance.   After that, it's about performance.
skb

I expect to see the provider to put some effort in how she present herself on the web.

1) They are often swiped from somewhere else for use by scammers.

2) Professional photographers use every trick in the book to flatter their subject. That makes me wonder what's being obscured.

3) Few people look quite as good as they do in their glamor photos, so it's almost a guarantee of disappointment.

4) The difference between a hot and fun provider with pro photos and a hot and fun provider with self-shot candid ones is usually about $100, with no value added to her actual services.