I think I know what the problem is.  

Picture textures are applied "parametrically" in Bryce (and in pretty much all other rendering applications).  That means that the texture has been specifically mapped to that model.  Each point on the model has a corresponding point on the map that was created for it.

In addition, most really good low-poly models, will have a separate "bump map" to apply additional texture.  Same as with the map for color, every point on the map corresponds to a point on the model.

If you are creating your own models, you will have to create your own texture and bump maps using a UV Mapping program.  UV Mapper Classic is available for free, as are some other mappers, and there are several that are great and are not horribly expensive.

What the mapping program will generate is sort of an unwrapped wire frame image that you can take into your 2D program and use as a template for painting your own texture and bump.  Or, which you can take and place your photograph over and create your texture that way.  (Be careful, however, just trying to create bump by using the same photo in grey scale -- sometimes it works, sometimes it doesn't.)

What you can't do is just take a photo and slap it on the model, because the various points on the photo have no idea where on the model they are supposed to sit.  Also, you can't take a texture map for one model and slap it on another.  Either way ... you just get a mess. 

Could be worse, could be raining.