I have a collection of visio stencils, and I need a tool that can create a gif/jpeg,etc index of the stencils within it.
If not available, is there a tool that can create a thumbnail of each object within a given stencil?
Probably what you want is vsdump, which can be installed via the Synaptic Package Manager, or by:
sudo apt-get install vsdump
But be warned; this program dumps Visio files out as XMLs, not as JPGs. But this is still useful, as XML files can be opened by other diagramming programs like Dia (also installable from the Ubuntu repositories). I was unable to find a program that did a straight conversion from .vss to .jpg, so this is the next best thing.