nxt 5.0 works the way you’d like with decals in Rhino 5 SR13. The Rendered display mode also shows the decals and allows for editing the placement prior to rendering. There are move up and down buttons to reorder a list of multiple decals applied to an object too. Transparency can also be set in Properties>Decals and previewed in Rendered mode. Here’s a link to the latest v5 as well as nxt
http://www.rhino3d.com/download/rhino/5.0/sr
http://www.rhino3d.com/download/Flamingo/5.0/release