When changing a set usually you must find a image and then upload for each texture, which takes forever if you change sets as frequently as me. My suggestion is when you find your image you can keep uploading images on other textures. Once done you can press an upload button on the top that will upload all of the images loaded at once.

this is already a thing... click the "Textures (multiple)" button when in the shop.

^^ ineeed.
For this to work you would need to give your textures (Art) the names of the bodyparts they are on, so head, l_thigh, r_thigh, l_hand, groin. All those names.
You can find these names here, just click on template for the item you need to know it's name of, and in the link it's name is shown.

This has already been implemented. Closing.