making a wall hanging look 3D

I had made a picture about 20 years ago.  It was done with preprinted material and I had somehow made it 3D.  I remember stitching around the areas I wanted to pop out, but I don't remember the details of how I did that.  I then remember stretching it over a frame to make it tight.  Do you know how that was done?  Do you put muslin as a backing with batting in between?  When I tried it on some material it didn't seem to work well.  Do you somehow stuff the areas?  I have another preprinted piece of material that has pumpkins and such on it and I thought it would be cute to use this technique with.
I hope that someone will know.
Thanks
sandy

I think the technique you're referring to is called trapunto.  I haven't ever done it myself, but I'll bet if you did a web search for trapunto you could find some details.  Good luck!