I actually had to go an look up the various web/javascript smalltalks -- it looks like a few of them are live and well -- but more importantly the Lively Kernel does offer a parts bin with basic shapes, and a right click halo that allows for modification -- but lively kernel could be made to look prettier by borrowing from here...:

  http://www.lively-kernel.org/

Note Lively isn't Smalltalk... but with OMeta[1] it sort of is: http://www.youtube.com/watch?v=f2dyLKP_xJc

[1] http://tinlizzie.org/ometa/

If you find [1] interesting you might also like:

http://www.vpri.org/vp_wiki/index.php/Main_Page