Just because, a my friend requested this and I need to update.
Icons are on the way! But for now...
This is an example of a credited icon:
To add a LJ username credit to an icon use the LJ user code. Make sure to type in the code to the comment section, not the keywords, because it wont work (because its a bitch) the code is shown in the highlighted section of the image above. make sure not to put the username in "quotation marks", as usual HTML because this screws things up.
Hope this was helpful! Any further questions let me know!