About the only thing I can think of is to have a thread reading the images ahead of time and stuffing the pixbufs into a hash. Of course, with alot of images, that hash can get huge. Using it with iconview seems to be the hassle.

If the images are relatively constant, why not use a separate script that reads all the images, puts them into pixbufs, stashes them into a hash, then saves it as a Storable db. You can even store the thumbnail for the image too. Then when you run your program, it will just slurp in all the pixbufs from the Storable db.

If you want speed, I think displaying alot of images in a Liststore is not the right way to go. I faced the same problem in Gtk2-thumbnail-previewer. If I wsan't so lazy ( or was getting paid :-)) I would work out a way to preload with Storable, or if the images changed alot, use a thread to be making the pixbufs, and after it made the first subdir, continue on with others. But there is one catch, what if the user clicks on a subdir that hasn't been processed yet, you may need 2 threads...one for background work, and one for an unexpected click.

All in all, I think preloading them with Storable, will be the fastest. That way you only read the files once from disk, and combine them all into one big Storable db. The Storable db will load very fast, as it is only a single file.