Another great bit of DIY inspiration from Evil Twin. I love the small details in the lookbooks that get my DIY brain all juiced up! These leggings look like a pretty simple undertaking, in fact I saw a girl at Glastonbury rocking some she has made herself. Grab a pair of dark opaque tights (the thicker the better so they don't rip), put them on and mark with chalk where you would want the 'suspenders' to sit. I would probably make the suspenders thinner and barely hanging on - maybe an inch at the front and back and I would make the cut out a bit more horizontal and higher up the leg - I have a feeling that would make your legs look longer. Take them off and get cutting!
Image: Evil Twin