Copyrighted material, be it images or text, are the sole property of the creator of the material or the current holder of the copyright.
In most cases this material is able to be used by anyone as long as it is not for profit or it is used with permission. For profit use requires that some sort of monies is returned to the copyright holder for the rights to use their material.
Not for profit use is another matter and is most usually available for use BUT somewhere it should be clearly noted somewhere in your own design that the material/copyright being used belongs to whoever holds the copyright.
This applies to room entries or website text as it is not usually practiced to have such posted for avatars, character tags, or coding used within rooms.
For example the room Aftermath in Themes:
*The Morrow Project is Copyrighted and owned by Timeline, Ltd. This content is in no way intended to infringe on any Copyright(s).
All content is for non-commercial individual use only.
If you are not sure if the material you are using is copyrighted you should be able to Google the main corporate site of the publisher and there you should find something that speaks of their copyright holding. But beware, just because it's not easily found does not mean the copyright does not exist so you would be using the material at your own risk should the holder not wish their material being used. Exercise on the side of caution and put it somewhere.
When it comes to overly changing or manipulating copyrighted material, more often than not that requires written permission from the copyright holder. This means images or text.
If you find a copyright that specifically states it is NOT to be used in any way whatsoever then you should by NO means use the material or you could face severe penalties and/or fines. Copyright holders such as that almost always have persons in their employ that purposely look for anyone using their material without permission or using it at all.
It all comes down to if you have to ask then you already know the answer and should, as stated above, exercise on the side of caution and protect yourself and Portal of Dreams.
Violation of copyright/trademark laws are no light matter and we at Portal of Dreams want all that call it home to have a carefree and great time while spending their time here.