Have a look at latest SVN. It implements a dropdown menu in pencil/pen toolbar to select various shapes which are applied instantly after finishing a path. At present it has the options "None", "Clipboard", "Crescendo" and "Decrescendo". The latter two are just offhand descriptions for very long triangles (give it a try and the meaning will become clear :) ).
That's awesome! I can't wait to check them out once I get home! :D
I also agree that text descriptions are fine for now. I suggest including some generic shapes once you figure out how to do the image drop-downs. I've made a few for personal use:
http://img84.imageshack.us/img84/471/rect2864az5.png
I doubt the more complex ones will be needed, but shapes such as double-lines, stitches, even rope and chain could be included. Does anybody needs me to make a few? What's the size of defaults?
By the way, is it me, or is the mailing list archive buggy?