Different Default Icons
Short, concise description of the idea
Have the option to have a default icon for postings, and another default icon for comments.
Full description of the idea
Perhaps it's just me but I like to post icons with a picture of myself, but reply to icons with some character of some sort. I think it would pretty slick if Livejournal in your icon menu allowed you to specify one icon to be your default icon when writing an entry, and then another icon to be your default when posting a comment. Or, just a general default icon for those who wouldn't care.
An ordered list of benefits
An ordered list of problems/issues involved
An organized list, or a few short paragraphs detailing suggestions for implementation