In place of keywords for this icon, I chose to type the username of the person who made it. This is one way of crediting, and used to be the primary way to go about it. However, LJ has since added a new feature, which serves the purpose of crediting quite well. The feature in question, of course, is as follows:
2. Crediting in Your Comments
As I go to upload this icon, I type in what I want my keywords to be (in this case, I choose to go with simply "sleepy."), and in the Comments section, I type in the code that links to triptochinatown's journal.
Look how nice that icon looks, with the username there like that!
*NOTE: Both icons used in this tutorial are from this set.