Ah, now you're trying to tell a *story,* or at least communicate an idea more involved than "Pretty girl in bed." (Not that that story isn't a classic.) For that we need more visual cues. An empty space can be an invitation, a challenge, a warning, or just an oversight. (If it's my picture, bet on #4.)
Have a look at this:
Now, this image has problems, but I think it's right on topic for this concept. Here we have some empty seat space next to the model. This keeps her from being centered, which is why I was shooting from this angle, but her hand placed on the couch beside her, and her inquisitive look, communicates to the viewer. (At least if I'm the viewer, it does. Your mileage may vary.) "Would you like to sit down?" is the idea I get. ("Yes, yes I would," is the appropriate answer.)
To make the idea even more explicit, I should have moved the frame even more to camera right and showed the entire "landing area" where the hypothetical viewer would sit, and the model could have used a bit more implication in her expression, perhaps a faint but welcoming smile.
Once you start doing concepts like this, the model becomes an actress and the photographer a director, shooting a movie that's 1/100th of a second long. That's not a lot of time to get an idea across, so you have to communicate it strongly. Not that you can't be subtle - an unsubtle way to do this would have been to have had the model "patting" the seat and crooking a finger on her other hand in the classic "come here" gesture, perhaps even with an exaggerated wink. But if you have a clear idea to communicate, you must communicate it clearly. (Ambiguity is in the advanced class.)