I see a lot of bases made from tracing over images found on google, photobucket, hentai sites, any place you could possibly find a pretty little image. While some of these bases are beautiful, I generally try to avoid them because I don't want to get caught up in potential legal battles.
"What are you talking about?"
Finding a random image and tracing it (or copying, for those who use them as references and keep pretty much every aspect the same) without getting written permission from the original artist of the image you're using is theft. It doesn't matter if it's on a public website or not. It belongs to the artist and is not for your use unless the artist states such.
"There was no stated copyright"
That doesn't matter. Legally, if a person produces a piece of art (written, sketched, painted, etc.) it belongs to them and nobody else has the right to use it without the artist's express permission. It doesn't matter if the artist dished out money to get their image copyrighted or not. By law, once the art is created it is instantly copyrighted to the artist. Paying for a copyright is mostly just a precaution for businesses.
"But I linked to the original in my description"
Sorry, but crediting is not the same thing as getting legal permission from the creator of the original image. Even if you link to the original, without written permission from the artist you are stealing. If you did not get permission, you are a criminal and you can be sued for copyright infringement if the original artist so wishes (believe me, I will sue people I find using my art).
So you see not only is it rude to use other peoples' art to create a base, it is also illegal. Happy trails.