Crediting is easy and I don't know why some people can't seem to manage it. However, if you are one of those dumb-as-a-brick people, or your just new to LJ, here are some instructions.
For Icons:
Icons should be credited in the "keywords" or "comment" box when you upload them. That is, somewhere in those text areas should be the words "made by:" or "credited to:" or even just "credit:" followed by my username. You can credit me as either
ameliaglitter or
seraphsong. Here is an example of how I credit userpics in my personal journal:
For Other LJ Graphics:
Such as colorbars, headers, friends only banners, backgrounds, mood themes etc. Credit should be given in your user profile with a link back to this journal. The words "mood theme by:" or "background by:" is simple, elegant and doesn't take up a lot of space. You may also use my pretty little button to link back to this journal.
To Use Graphics On Other Journals:
If you are using my icons on DeadJournal or GreatestJournal or CopiedOffofLJJournal there is a similar setup as there is on LJ, I'm sure (I don't actually know, I'm a hardcore LJ addict). Somewhere put "credit: seraphsong @ LiveJournal" or "credit: ameliaglitter @ LiveJournal" and provide a link back to this journal if possible.
For Use on Message Boards
If the message board has a user profile or signature put "credit: seraphsong @ LiveJournal" and provide a link back to this journal.
On Everything Else
Providing a link to this journal is the minimal crediting you can do and not be considered an evil graphic thief.