I create landscape designs and use objects I create in various projects. I use Micrografx Picture Publisher right now and I set up a document where I store all my live objects. They are just layers that are not flattened, so I can go to it, copy it and paste it to my new document.
When I was trying to learn photoshop, they called this a palette. I think in Gimp it would be something like the brushes library or the textures library.
Reading the user dox, I noticed these layers/objects are to be saved as channels. They would all be rgba since the surround image is transparent. I have found I can take the Micrografx .tifs and import them into Gimp and they show up with a transparent background.
I suppose I could save each object as a tif with a transparent background, but I have about 200 of these objects and don't want to have to open separate files every time I need to use one.