Batman's suit is the Flexxsuit for M4 by Xurge3D. I added a displacement map myself to get the bat to sink into the chest. I also use the same suit for my Sith character that I named, affectionately, Darth Xurge, just minus the bat. The cowl can be found over at
www.sharecg.com and the cape is the ODS Dynamic Cape, retextured to match the cowl, which can be found over at
www.animotions.com, both of which are free. I'd consider doing the hand on hand thing because you're right, it's an incredible idea that I hadn't thought of, but the way the cape drapes over Batman in the cloth room in Poser would probably make it drape over her as well and cover up both hands. Haven't quite figured out how to get it to drape over the shoulders yet. It always hangs in front.
Wonder Woman's costume is a texture set for the V4 Bodysuit and the breastplate, bracers, belt, and boots are all conforming pieces that can also be found at
www.sharecg.com for free.
I honestly can't remember where I got the textures for Robin and Nightwing in my Batfamily images, but if you search hard enough, you'll probably find them. It's just been way too long since I picked them up for me to remember where I got them. Robin's cape is also the ODS Dynamic Cape, retextured to match his neck and blended together in Photoshop. If you're unfamiliar with the cloth room in Poser, don't be daunted. The cape comes with a step by step PDF instruction file, so you can't go wrong, and you can also apply what it teaches you to other dynamic clothing.
If you're wanting to learn how to make some amazing 3D art, you came to the right place. If it wasn't for the incredibly helpful and talented artists that I've made friends with here I probably still wouldn't know what I'm doing.
Hope all this helps.