Don't forget either that unless you have lots of toolbar buttons or other such objects to fill, its possible to get by with very few icons beyond your own unique application icon and system icons. (Remember to call them from existing libraries on the user's machine, not repackage them, keep the lawyers happy.)
Having too many icons can be just as bad as having some ugly ones. Many guidelines state that if you can't have professional looking icons have some whitespace instead. It can help to keep the interface light and feel uncluttered.
