In the Viewport Canvas Tool we cannot select VrayBitmap Textures, only its mapping source map slot.
For easy of use, please add support in Viewport Canvas for these kind of textures. The 3dsmax's own alternative Bitmap loaders aren't currently supported aswell (Uber Bitmap, Bitmap Lookup). I suppose other renderers are having the same problem aswell.
If the problem lies within VrayBitmap, please communicate this so I can contact Chaosgroup for a feature request.
