I have attempted this in the past and was able to apply decals as a texture map to a part BUT it does not show up in drawings. I need to document location of safety decals on our equipment and I have not found a good way of doing it.
i hope the decal you want to put is in some regular shape (circular or rectangular) if yes, then just make a curve of that shape so that you get the location dimension in drawing and use note to discribe the rest