there is a problem if I take a photo (signature with measures of 400x150) and change colors and some more details, is not a copy of it true? that is if I put flashes etc, i find this diadem on Google, and i made this one:
https://jyl013.deviantart.com/art/Necromancer-Forum-Signature-198133713

what i made :
http://i66.tinypic.com/vy2hrp.jpg

Using a premade signature as base for your signature without permission of the owner of the image is considered ripping.
Your stealing someone else's design, adding to it, and claiming it as your own.
If you were personally given permission to make edits to their image, or if they stated that their image is free to use and edit, then it's acceptable.