All Thelotornis (twig snakes) are incredibly lethal. They are right up there with Dispholidus (boomslangs). The only difference between twigs and slangs is that twigs have no AV available. If you have a serious envenomation, you might as well kiss your rear goodbye. Symptoms from twigsnake venom are somewhat similar to a boomslang envenomation: heavy internal bleeding. You may not notice anything for a day or so, then collapse from the hemorrhaging.
As for pictures of these snakes, you can go to venomousreptiles.org and check the photo gallery under the "medically important colubrid" section. Tomas Eimermacher, a frequenter of these forums under the name NightFlight99, keeps I believe two, maybe more, of the Thelotornis species. He has numerous pictures on venomousreptiles.org of his twigsnakes, even some feeding pics I believe. You can also check Mardi Snipes' website at coastalreptiles.com. In his photo gallery, I believe he has some twig snake pictures. I hope this was of some assistance to you.
-Chance