Oddly enough, stripper heels/shoes work wonders for making your thighs look thinner and your legs look longer overall. They are hideously uncomfortable, but with certain poses, they can make your legs look epic! Try wearing a pair of platform stripper heels, stand shoulder width apart (no more, hard to balance), and face to the side. Put one leg slightly forward, and lean forward about 1/3 to 1/2 way over, then go for your look, and shoot. Practice in front of the mirror...looks STUPID but it works! ALOT! LOL I've done all this stuff, and it did amazing things for my legs. Try to avoid high boots...they make your legs look lots shorter/thicker.
You would need a photog that knows corrective lighting. The way it's done is to cast a shadow lengthwise on your legs (this is hard to explain) which gives the impression they are smaller than they are. Or do it in PS with liquify.
I think your legs are rather nice, BUT if you're concerned about it-- I second the high heels. Something particularly high (heel not necessarily platform), and preferable a shoe that doesn't have a strap across your ankle (this interrupts the line of the leg making it look shorter). Shorter skirts might be a hit or a miss.
Try looser fabric, avoid things that are tight on your legs. Also try not to do platforms. Skinny heels without a strap on your ankle like a previous poster already said will make your legs look longer and slimmer.
Image 9437 It's all about the angles. You have the leg in a toe pose giving you instant slim. Compare this image to the rest and you'll see what I'm talking about. I have thick thighs and short legs and no matter what I do they stay that way. It's in my family so I have to just make it work. I do a lot of medium shots. Never leave your legs stick straight. I find that relaxing and even bending your leg slightly gives them an instant slimmer touch.
If the photographer shoots from a position closer to the ground your legs will look longer. Also, heels help, as well as keeping the largest part of you tilted away from the camera will help as well (ie, tilting your hips away from the camera and tilting your top half towards it). Skirts to the knee will look better than tight shorts, as well as straight-leg pants (jeans or slacks). For skirts a more A-line cut would work best as it pulls away from you hips and doesn't put the emphasis on them.
Most have already been mentioned but definately looser skirts (This isn't a bad length), High heels (Preferably spikes, no strap), turn slightly sideways (but without bending the knee) and extend the on camera leg slightly towards the camera. Flexing the butt cheeks (hard!) will tend to tighten both the calves and the thighs, giving better muscular definition.