The concepts aren't as important as a good photographer (lighting is a lot more complex that most people think) and a good hamu artist (lighting is a lot more complex than most people think)
Personally I feel the best photos for something like this are good hight quality, but untouched shots. Photoshop tweaks are very common, but also very noticeable. Remember while you are selling a fantasy, we are still buying a reality.
That said if you are asking for concept ideas. You seems light fun, bubbly based on the previous photos if that is accurate stick with that don't go for dark, smoldering, and sultry if that isn't you.
I like the naughty at the beach idea mentioned above. Yoga / contortion poses can be done well, but can take a long time to get the light and shadowing right as all kinds of body parts aren't where they normally are. The school girl costume is a bit played, but a real co-ed look may work, slut up a UT shirt with the prerequisite denim micro and cowboy boots, or the always popular xs sweater atop skinny jeans.
As far as positions, trust the photographer, a good rule of thumb the more unnatural and uncomfortable a pose feels, the better the shot.
If you have any question, or want further advice i'm just a PM away.
